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	$36.95	11.308%	$41.1283	$41.13	$41.15	$41.10
Purchase #2	$18.71	11.707%	$20.9004	$20.90	$20.90	$20.90
Purchase #3	$24.39	4.288%	$25.4358	$25.44	$25.45	$25.40
Purchase #4	$118.51	11.738%	$132.4207	$132.42	$132.40	$132.40
Purchase #5	$72.79	10.308%	$80.2932	$80.29	$80.30	$80.30
Purchase #6	$148.42	13.419%	$168.3365	$168.34	$168.35	$168.30
Purchase #7	$54.83	4.299%	$57.1871	$57.19	$57.20	$57.20
7 purchase totals =	$474.60		$525.7020	$525.71	$525.75	$525.60