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	$168.86	11.606%	$188.4579	$188.46	$188.45	$188.50
Purchase #2	$53.56	11.272%	$59.5973	$59.60	$59.60	$59.60
Purchase #3	$239.70	7.122%	$256.7714	$256.77	$256.75	$256.80
Purchase #4	$81.70	8.214%	$88.4108	$88.41	$88.40	$88.40
Purchase #5	$87.77	8.516%	$95.2445	$95.24	$95.25	$95.20
Purchase #6	$246.47	7.450%	$264.832	$264.83	$264.85	$264.80
Purchase #7	$158.25	8.369%	$171.4939	$171.49	$171.50	$171.50
7 purchase totals =	$1,036.31		$1,124.8078	$1,124.80	$1,124.80	$1,124.80