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	$130.43	7.411%	$140.0962	$140.10	$140.10	$140.10
Purchase #2	$17.51	11.824%	$19.5804	$19.58	$19.60	$19.60
Purchase #3	$155.78	12.597%	$175.4036	$175.40	$175.40	$175.40
Purchase #4	$237.34	7.645%	$255.4846	$255.48	$255.50	$255.50
Purchase #5	$141.40	6.796%	$151.0095	$151.01	$151.00	$151.00
Purchase #6	$145.82	4.641%	$152.5875	$152.59	$152.60	$152.60
Purchase #7	$221.91	6.473%	$236.2742	$236.27	$236.25	$236.30
7 purchase totals =	$1,050.19		$1,130.4360	$1,130.43	$1,130.45	$1,130.50