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	$68.45	11.424%	$76.2697	$76.27	$76.25	$76.30
Purchase #2	$178.93	6.273%	$190.1543	$190.15	$190.15	$190.20
Purchase #3	$207.89	10.360%	$229.4274	$229.43	$229.45	$229.40
Purchase #4	$67.82	6.699%	$72.3633	$72.36	$72.35	$72.40
Purchase #5	$6.63	5.244%	$6.9777	$6.98	$7.00	$7.00
Purchase #6	$159.49	12.592%	$179.573	$179.57	$179.55	$179.60
Purchase #7	$88.53	12.637%	$99.7175	$99.72	$99.70	$99.70
7 purchase totals =	$777.74		$854.4829	$854.48	$854.45	$854.60