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	$35.64	4.613%	$37.2841	$37.28	$37.30	$37.30
Purchase #2	$149.39	12.148%	$167.5379	$167.54	$167.55	$167.50
Purchase #3	$66.40	9.832%	$72.9284	$72.93	$72.95	$72.90
Purchase #4	$55.73	5.446%	$58.7651	$58.77	$58.75	$58.80
Purchase #5	$218.44	12.111%	$244.8953	$244.90	$244.90	$244.90
Purchase #6	$167.77	11.812%	$187.587	$187.59	$187.60	$187.60
Purchase #7	$250.89	7.505%	$269.7193	$269.72	$269.70	$269.70
7 purchase totals =	$944.26		$1,038.7171	$1,038.73	$1,038.75	$1,038.70