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	$42.95	9.853%	$47.1819	$47.18	$47.20	$47.20
Purchase #2	$245.78	12.252%	$275.893	$275.89	$275.90	$275.90
Purchase #3	$189.77	12.332%	$213.1724	$213.17	$213.15	$213.20
Purchase #4	$26.48	7.581%	$28.4874	$28.49	$28.50	$28.50
Purchase #5	$113.33	8.825%	$123.3314	$123.33	$123.35	$123.30
Purchase #6	$26.66	4.225%	$27.7864	$27.79	$27.80	$27.80
Purchase #7	$41.63	6.341%	$44.2698	$44.27	$44.25	$44.30
7 purchase totals =	$686.60		$760.1223	$760.12	$760.15	$760.20