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	$35.48	4.411%	$37.045	$37.05	$37.05	$37.00
Purchase #2	$156.46	5.474%	$165.0246	$165.02	$165.00	$165.00
Purchase #3	$236.45	7.786%	$254.86	$254.86	$254.85	$254.90
Purchase #4	$198.86	9.829%	$218.4059	$218.41	$218.40	$218.40
Purchase #5	$47.96	12.173%	$53.7982	$53.80	$53.80	$53.80
Purchase #6	$46.50	9.192%	$50.7743	$50.77	$50.75	$50.80
Purchase #7	$170.33	3.142%	$175.6818	$175.68	$175.70	$175.70
7 purchase totals =	$892.04		$955.5898	$955.59	$955.55	$955.60