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	$61.56	4.679%	$64.4404	$64.44	$64.45	$64.40
Purchase #2	$36.37	3.110%	$37.5011	$37.50	$37.50	$37.50
Purchase #3	$221.99	12.842%	$250.498	$250.50	$250.50	$250.50
Purchase #4	$241.46	12.760%	$272.2703	$272.27	$272.25	$272.30
Purchase #5	$214.47	12.132%	$240.4895	$240.49	$240.50	$240.50
Purchase #6	$78.97	8.182%	$85.4313	$85.43	$85.45	$85.40
Purchase #7	$101.86	4.562%	$106.5069	$106.51	$106.50	$106.50
7 purchase totals =	$956.68		$1,057.1375	$1,057.14	$1,057.15	$1,057.10