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	$166.33	5.109%	$174.8278	$174.83	$174.85	$174.80
Purchase #2	$58.27	11.388%	$64.9058	$64.91	$64.90	$64.90
Purchase #3	$69.75	11.741%	$77.9393	$77.94	$77.95	$77.90
Purchase #4	$34.45	8.665%	$37.4351	$37.44	$37.45	$37.40
Purchase #5	$35.89	7.566%	$38.6054	$38.61	$38.60	$38.60
Purchase #6	$248.91	9.781%	$273.2559	$273.26	$273.25	$273.30
Purchase #7	$53.92	12.439%	$60.6271	$60.63	$60.65	$60.60
7 purchase totals =	$667.52		$727.5964	$727.62	$727.65	$727.50