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	$73.32	4.864%	$76.8863	$76.89	$76.90	$76.90
Purchase #2	$80.29	7.445%	$86.2676	$86.27	$86.25	$86.30
Purchase #3	$79.32	5.745%	$83.8769	$83.88	$83.90	$83.90
Purchase #4	$246.50	7.563%	$265.1428	$265.14	$265.15	$265.10
Purchase #5	$48.27	13.657%	$54.8622	$54.86	$54.85	$54.90
Purchase #6	$82.37	8.349%	$89.2471	$89.25	$89.25	$89.20
Purchase #7	$232.51	10.113%	$256.0237	$256.02	$256.00	$256.00
7 purchase totals =	$842.58		$912.3066	$912.31	$912.30	$912.30