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	$104.82	3.539%	$108.5296	$108.53	$108.55	$108.50
Purchase #2	$176.46	4.825%	$184.9742	$184.97	$184.95	$185.00
Purchase #3	$9.62	9.552%	$10.5389	$10.54	$10.55	$10.50
Purchase #4	$225.33	8.755%	$245.0576	$245.06	$245.05	$245.10
Purchase #5	$143.59	11.166%	$159.6233	$159.62	$159.60	$159.60
Purchase #6	$133.39	6.573%	$142.1577	$142.16	$142.15	$142.20
Purchase #7	$174.85	4.444%	$182.6203	$182.62	$182.60	$182.60
7 purchase totals =	$968.06		$1,033.5016	$1,033.50	$1,033.45	$1,033.50