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	$55.35	10.865%	$61.3638	$61.36	$61.35	$61.40
Purchase #2	$80.56	4.853%	$84.4696	$84.47	$84.45	$84.50
Purchase #3	$6.27	8.630%	$6.8111	$6.81	$6.80	$6.80
Purchase #4	$73.45	6.679%	$78.3557	$78.36	$78.35	$78.40
Purchase #5	$99.74	4.457%	$104.1854	$104.19	$104.20	$104.20
Purchase #6	$6.72	11.251%	$7.4761	$7.48	$7.50	$7.50
Purchase #7	$160.95	11.769%	$179.8922	$179.89	$179.90	$179.90
7 purchase totals =	$483.04		$522.5539	$522.56	$522.55	$522.70