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	$143.86	3.798%	$149.3238	$149.32	$149.30	$149.30
Purchase #2	$48.43	6.219%	$51.4419	$51.44	$51.45	$51.40
Purchase #3	$81.32	9.795%	$89.2853	$89.29	$89.30	$89.30
Purchase #4	$60.43	6.184%	$64.167	$64.17	$64.15	$64.20
Purchase #5	$230.39	6.501%	$245.3677	$245.37	$245.35	$245.40
Purchase #6	$94.33	12.259%	$105.8939	$105.89	$105.90	$105.90
Purchase #7	$211.25	9.109%	$230.4928	$230.49	$230.50	$230.50
7 purchase totals =	$870.01		$935.9724	$935.97	$935.95	$936.00