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	$89.82	7.466%	$96.526	$96.53	$96.55	$96.50
Purchase #2	$172.89	11.264%	$192.3643	$192.36	$192.35	$192.40
Purchase #3	$99.67	12.361%	$111.9902	$111.99	$112.00	$112.00
Purchase #4	$56.61	5.494%	$59.7202	$59.72	$59.70	$59.70
Purchase #5	$224.34	9.613%	$245.9058	$245.91	$245.90	$245.90
Purchase #6	$117.52	5.654%	$124.1646	$124.16	$124.15	$124.20
Purchase #7	$226.35	10.486%	$250.0851	$250.09	$250.10	$250.10
7 purchase totals =	$987.20		$1,080.7562	$1,080.76	$1,080.75	$1,080.80