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	$191.28	4.677%	$200.2262	$200.23	$200.25	$200.20
Purchase #2	$182.83	3.602%	$189.4155	$189.42	$189.40	$189.40
Purchase #3	$108.89	6.132%	$115.5671	$115.57	$115.55	$115.60
Purchase #4	$207.79	11.344%	$231.3617	$231.36	$231.35	$231.40
Purchase #5	$55.75	12.714%	$62.8381	$62.84	$62.85	$62.80
Purchase #6	$125.89	11.865%	$140.8268	$140.83	$140.85	$140.80
Purchase #7	$108.46	11.873%	$121.3375	$121.34	$121.35	$121.30
7 purchase totals =	$980.89		$1,061.5729	$1,061.59	$1,061.60	$1,061.50