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	$80.36	11.232%	$89.386	$89.39	$89.40	$89.40
Purchase #2	$36.89	7.111%	$39.5132	$39.51	$39.50	$39.50
Purchase #3	$26.34	4.324%	$27.4789	$27.48	$27.50	$27.50
Purchase #4	$171.41	13.751%	$194.9806	$194.98	$195.00	$195.00
Purchase #5	$204.62	6.496%	$217.9121	$217.91	$217.90	$217.90
Purchase #6	$89.76	5.545%	$94.7372	$94.74	$94.75	$94.70
Purchase #7	$65.67	7.264%	$70.4403	$70.44	$70.45	$70.40
7 purchase totals =	$675.05		$734.4483	$734.45	$734.50	$734.40