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	$130.90	8.305%	$141.7712	$141.77	$141.75	$141.80
Purchase #2	$22.64	13.664%	$25.7335	$25.73	$25.75	$25.70
Purchase #3	$98.47	4.857%	$103.2527	$103.25	$103.25	$103.30
Purchase #4	$221.29	8.801%	$240.7657	$240.77	$240.75	$240.80
Purchase #5	$138.87	10.684%	$153.7069	$153.71	$153.70	$153.70
Purchase #6	$193.37	11.269%	$215.1609	$215.16	$215.15	$215.20
Purchase #7	$179.57	11.858%	$200.8634	$200.86	$200.85	$200.90
7 purchase totals =	$985.11		$1,081.2543	$1,081.25	$1,081.20	$1,081.40