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	$142.77	6.747%	$152.4027	$152.40	$152.40	$152.40
Purchase #2	$80.59	11.276%	$89.6773	$89.68	$89.70	$89.70
Purchase #3	$37.79	5.143%	$39.7335	$39.73	$39.75	$39.70
Purchase #4	$60.39	8.673%	$65.6276	$65.63	$65.65	$65.60
Purchase #5	$64.38	10.798%	$71.3318	$71.33	$71.35	$71.30
Purchase #6	$23.34	9.483%	$25.5533	$25.55	$25.55	$25.60
Purchase #7	$32.39	4.351%	$33.7993	$33.80	$33.80	$33.80
7 purchase totals =	$441.65		$478.1255	$478.12	$478.20	$478.10