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	$87.87	8.628%	$95.4514	$95.45	$95.45	$95.50
Purchase #2	$212.61	4.642%	$222.4794	$222.48	$222.50	$222.50
Purchase #3	$27.82	12.166%	$31.2046	$31.20	$31.20	$31.20
Purchase #4	$200.63	10.805%	$222.3081	$222.31	$222.30	$222.30
Purchase #5	$79.73	11.831%	$89.1629	$89.16	$89.15	$89.20
Purchase #6	$14.97	11.650%	$16.714	$16.71	$16.70	$16.70
Purchase #7	$202.98	8.825%	$220.893	$220.89	$220.90	$220.90
7 purchase totals =	$826.61		$898.2134	$898.20	$898.20	$898.30