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	$203.32	12.787%	$229.3185	$229.32	$229.30	$229.30
Purchase #2	$67.59	8.494%	$73.3311	$73.33	$73.35	$73.30
Purchase #3	$228.45	11.654%	$255.0736	$255.07	$255.05	$255.10
Purchase #4	$155.91	8.850%	$169.708	$169.71	$169.70	$169.70
Purchase #5	$152.72	6.417%	$162.52	$162.52	$162.50	$162.50
Purchase #6	$83.42	6.410%	$88.7672	$88.77	$88.75	$88.80
Purchase #7	$160.96	4.547%	$168.2789	$168.28	$168.30	$168.30
7 purchase totals =	$1,052.37		$1,146.9973	$1,147.00	$1,146.95	$1,147.00