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	$99.72	13.521%	$113.2031	$113.20	$113.20	$113.20
Purchase #2	$205.73	8.306%	$222.8179	$222.82	$222.80	$222.80
Purchase #3	$64.79	3.118%	$66.8102	$66.81	$66.80	$66.80
Purchase #4	$84.74	13.259%	$95.9757	$95.98	$96.00	$96.00
Purchase #5	$205.85	6.610%	$219.4567	$219.46	$219.45	$219.50
Purchase #6	$128.39	9.225%	$140.234	$140.23	$140.25	$140.20
Purchase #7	$142.86	6.323%	$151.893	$151.89	$151.90	$151.90
7 purchase totals =	$932.08		$1,010.3906	$1,010.39	$1,010.40	$1,010.40