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	$57.88	7.418%	$62.1735	$62.17	$62.15	$62.20
Purchase #2	$114.82	8.687%	$124.7944	$124.79	$124.80	$124.80
Purchase #3	$60.89	4.268%	$63.4888	$63.49	$63.50	$63.50
Purchase #4	$158.47	9.109%	$172.905	$172.91	$172.90	$172.90
Purchase #5	$243.66	9.494%	$266.7931	$266.79	$266.80	$266.80
Purchase #6	$90.66	10.665%	$100.3289	$100.33	$100.35	$100.30
Purchase #7	$203.80	11.516%	$227.2696	$227.27	$227.25	$227.30
7 purchase totals =	$930.18		$1,017.7533	$1,017.75	$1,017.75	$1,017.80