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	$117.57	3.751%	$121.9801	$121.98	$122.00	$122.00
Purchase #2	$109.98	4.170%	$114.5662	$114.57	$114.55	$114.60
Purchase #3	$243.34	5.586%	$256.933	$256.93	$256.95	$256.90
Purchase #4	$116.28	5.486%	$122.6591	$122.66	$122.65	$122.70
Purchase #5	$209.66	6.323%	$222.9168	$222.92	$222.90	$222.90
Purchase #6	$138.48	9.373%	$151.4597	$151.46	$151.45	$151.50
Purchase #7	$142.28	12.300%	$159.7804	$159.78	$159.80	$159.80
7 purchase totals =	$1,077.59		$1,150.2953	$1,150.30	$1,150.30	$1,150.40