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	$198.74	12.455%	$223.4931	$223.49	$223.50	$223.50
Purchase #2	$145.93	12.778%	$164.5769	$164.58	$164.60	$164.60
Purchase #3	$6.99	9.640%	$7.6638	$7.66	$7.65	$7.70
Purchase #4	$65.59	10.721%	$72.6219	$72.62	$72.60	$72.60
Purchase #5	$246.34	4.301%	$256.9351	$256.94	$256.95	$256.90
Purchase #6	$196.62	7.456%	$211.28	$211.28	$211.30	$211.30
Purchase #7	$191.72	7.495%	$206.0894	$206.09	$206.10	$206.10
7 purchase totals =	$1,051.93		$1,142.6602	$1,142.66	$1,142.70	$1,142.70