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	$191.76	4.539%	$200.464	$200.46	$200.45	$200.50
Purchase #2	$14.39	7.669%	$15.4936	$15.49	$15.50	$15.50
Purchase #3	$123.91	4.554%	$129.5529	$129.55	$129.55	$129.60
Purchase #4	$74.36	5.530%	$78.4721	$78.47	$78.45	$78.50
Purchase #5	$248.96	9.114%	$271.6502	$271.65	$271.65	$271.70
Purchase #6	$120.86	6.596%	$128.8319	$128.83	$128.85	$128.80
Purchase #7	$128.95	4.286%	$134.4768	$134.48	$134.50	$134.50
7 purchase totals =	$903.19		$958.9415	$958.93	$958.95	$959.10