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	$42.77	11.399%	$47.6454	$47.65	$47.65	$47.60
Purchase #2	$59.92	10.796%	$66.389	$66.39	$66.40	$66.40
Purchase #3	$157.74	6.745%	$168.3796	$168.38	$168.40	$168.40
Purchase #4	$88.25	4.107%	$91.8744	$91.87	$91.85	$91.90
Purchase #5	$73.49	11.753%	$82.1273	$82.13	$82.15	$82.10
Purchase #6	$50.48	13.186%	$57.1363	$57.14	$57.15	$57.10
Purchase #7	$137.33	3.107%	$141.5968	$141.60	$141.60	$141.60
7 purchase totals =	$609.98		$655.1488	$655.16	$655.20	$655.10