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	$217.54	13.207%	$246.2705	$246.27	$246.25	$246.30
Purchase #2	$235.71	3.319%	$243.5332	$243.53	$243.55	$243.50
Purchase #3	$145.72	8.362%	$157.9051	$157.91	$157.90	$157.90
Purchase #4	$137.45	9.452%	$150.4418	$150.44	$150.45	$150.40
Purchase #5	$59.81	9.637%	$65.5739	$65.57	$65.55	$65.60
Purchase #6	$248.83	6.170%	$264.1828	$264.18	$264.20	$264.20
Purchase #7	$64.27	11.332%	$71.5531	$71.55	$71.55	$71.60
7 purchase totals =	$1,109.33		$1,199.4604	$1,199.45	$1,199.45	$1,199.50