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	$29.30	12.261%	$32.8925	$32.89	$32.90	$32.90
Purchase #2	$249.96	4.486%	$261.1732	$261.17	$261.15	$261.20
Purchase #3	$197.90	3.816%	$205.4519	$205.45	$205.45	$205.50
Purchase #4	$113.33	8.627%	$123.107	$123.11	$123.10	$123.10
Purchase #5	$186.82	9.613%	$204.779	$204.78	$204.80	$204.80
Purchase #6	$207.47	3.481%	$214.692	$214.69	$214.70	$214.70
Purchase #7	$30.34	6.754%	$32.3892	$32.39	$32.40	$32.40
7 purchase totals =	$1,015.12		$1,074.4848	$1,074.48	$1,074.50	$1,074.60