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	$9.83	10.643%	$10.8762	$10.88	$10.90	$10.90
Purchase #2	$17.33	12.443%	$19.4864	$19.49	$19.50	$19.50
Purchase #3	$95.38	9.466%	$104.4087	$104.41	$104.40	$104.40
Purchase #4	$111.82	11.675%	$124.875	$124.88	$124.90	$124.90
Purchase #5	$131.85	13.865%	$150.131	$150.13	$150.15	$150.10
Purchase #6	$89.94	8.231%	$97.343	$97.34	$97.35	$97.30
Purchase #7	$211.50	10.745%	$234.2257	$234.23	$234.25	$234.20
7 purchase totals =	$667.65		$741.3460	$741.36	$741.45	$741.30