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	$185.33	3.301%	$191.4477	$191.45	$191.45	$191.40
Purchase #2	$245.33	11.444%	$273.4056	$273.41	$273.40	$273.40
Purchase #3	$128.44	6.358%	$136.6062	$136.61	$136.60	$136.60
Purchase #4	$116.61	7.650%	$125.5307	$125.53	$125.55	$125.50
Purchase #5	$110.71	5.423%	$116.7138	$116.71	$116.70	$116.70
Purchase #6	$141.29	7.775%	$152.2753	$152.28	$152.30	$152.30
Purchase #7	$156.67	5.639%	$165.5046	$165.50	$165.50	$165.50
7 purchase totals =	$1,084.38		$1,161.4839	$1,161.49	$1,161.50	$1,161.40