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	$7.32	3.332%	$7.5639	$7.56	$7.55	$7.60
Purchase #2	$187.73	3.483%	$194.2686	$194.27	$194.25	$194.30
Purchase #3	$41.54	9.556%	$45.5096	$45.51	$45.50	$45.50
Purchase #4	$219.75	11.494%	$245.0081	$245.01	$245.00	$245.00
Purchase #5	$61.77	3.831%	$64.1364	$64.14	$64.15	$64.10
Purchase #6	$106.79	5.482%	$112.6442	$112.64	$112.65	$112.60
Purchase #7	$54.48	13.652%	$61.9176	$61.92	$61.90	$61.90
7 purchase totals =	$679.38		$731.0484	$731.05	$731.00	$731.00