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	$93.62	7.356%	$100.5067	$100.51	$100.50	$100.50
Purchase #2	$63.36	6.515%	$67.4879	$67.49	$67.50	$67.50
Purchase #3	$164.60	12.598%	$185.3363	$185.34	$185.35	$185.30
Purchase #4	$215.80	8.521%	$234.1883	$234.19	$234.20	$234.20
Purchase #5	$86.83	10.206%	$95.6919	$95.69	$95.70	$95.70
Purchase #6	$139.40	5.644%	$147.2677	$147.27	$147.25	$147.30
Purchase #7	$100.90	9.675%	$110.6621	$110.66	$110.65	$110.70
7 purchase totals =	$864.51		$941.1409	$941.15	$941.15	$941.20