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	$229.75	11.167%	$255.4062	$255.41	$255.40	$255.40
Purchase #2	$47.79	11.655%	$53.3599	$53.36	$53.35	$53.40
Purchase #3	$67.32	5.829%	$71.2441	$71.24	$71.25	$71.20
Purchase #4	$140.77	4.678%	$147.3552	$147.36	$147.35	$147.40
Purchase #5	$143.57	6.484%	$152.8791	$152.88	$152.90	$152.90
Purchase #6	$233.30	12.410%	$262.2525	$262.25	$262.25	$262.30
Purchase #7	$177.80	6.621%	$189.5721	$189.57	$189.55	$189.60
7 purchase totals =	$1,040.30		$1,132.0691	$1,132.07	$1,132.05	$1,132.20