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	$130.32	11.386%	$145.1582	$145.16	$145.15	$145.20
Purchase #2	$209.33	6.208%	$222.3252	$222.33	$222.35	$222.30
Purchase #3	$48.27	7.204%	$51.7474	$51.75	$51.75	$51.70
Purchase #4	$93.41	12.309%	$104.9078	$104.91	$104.90	$104.90
Purchase #5	$172.86	12.735%	$194.8737	$194.87	$194.85	$194.90
Purchase #6	$141.88	4.778%	$148.659	$148.66	$148.65	$148.70
Purchase #7	$66.91	5.623%	$70.6723	$70.67	$70.65	$70.70
7 purchase totals =	$862.98		$938.3436	$938.35	$938.30	$938.40