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	$149.89	9.658%	$164.3664	$164.37	$164.35	$164.40
Purchase #2	$80.38	7.665%	$86.5411	$86.54	$86.55	$86.50
Purchase #3	$95.33	12.715%	$107.4512	$107.45	$107.45	$107.50
Purchase #4	$124.84	5.220%	$131.3566	$131.36	$131.35	$131.40
Purchase #5	$180.41	12.606%	$203.1525	$203.15	$203.15	$203.20
Purchase #6	$164.52	9.452%	$180.0704	$180.07	$180.05	$180.10
Purchase #7	$78.76	13.740%	$89.5816	$89.58	$89.60	$89.60
7 purchase totals =	$874.13		$962.5198	$962.52	$962.50	$962.70