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	$228.42	3.840%	$237.1913	$237.19	$237.20	$237.20
Purchase #2	$88.79	7.846%	$95.7565	$95.76	$95.75	$95.80
Purchase #3	$112.93	9.359%	$123.4991	$123.50	$123.50	$123.50
Purchase #4	$182.93	4.176%	$190.5692	$190.57	$190.55	$190.60
Purchase #5	$57.34	3.376%	$59.2758	$59.28	$59.30	$59.30
Purchase #6	$222.45	5.316%	$234.2754	$234.28	$234.30	$234.30
Purchase #7	$112.65	10.736%	$124.7441	$124.74	$124.75	$124.70
7 purchase totals =	$1,005.51		$1,065.3114	$1,065.32	$1,065.35	$1,065.40