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	$118.40	9.755%	$129.9499	$129.95	$129.95	$129.90
Purchase #2	$50.27	11.793%	$56.1983	$56.20	$56.20	$56.20
Purchase #3	$71.52	10.120%	$78.7578	$78.76	$78.75	$78.80
Purchase #4	$241.64	5.247%	$254.3189	$254.32	$254.30	$254.30
Purchase #5	$34.59	8.165%	$37.4143	$37.41	$37.40	$37.40
Purchase #6	$58.38	5.326%	$61.4893	$61.49	$61.50	$61.50
Purchase #7	$164.81	8.869%	$179.427	$179.43	$179.45	$179.40
7 purchase totals =	$739.61		$797.5555	$797.56	$797.55	$797.50