Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.35	13.500%	$160.4323	$160.43	$160.45	$160.40
Purchase #2	$125.30	4.201%	$130.5639	$130.56	$130.55	$130.60
Purchase #3	$179.79	11.482%	$200.4335	$200.43	$200.45	$200.40
Purchase #4	$145.28	4.789%	$152.2375	$152.24	$152.25	$152.20
Purchase #5	$134.98	3.284%	$139.4127	$139.41	$139.40	$139.40
Purchase #6	$108.32	3.354%	$111.9531	$111.95	$111.95	$112.00
Purchase #7	$202.46	10.238%	$223.1879	$223.19	$223.20	$223.20
7 purchase totals =	$1,037.48		$1,118.2209	$1,118.21	$1,118.25	$1,118.20