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	$153.98	11.167%	$171.1749	$171.17	$171.15	$171.20
Purchase #2	$149.33	8.365%	$161.8215	$161.82	$161.80	$161.80
Purchase #3	$93.72	12.352%	$105.2963	$105.30	$105.30	$105.30
Purchase #4	$100.44	8.248%	$108.7243	$108.72	$108.70	$108.70
Purchase #5	$239.94	11.572%	$267.7059	$267.71	$267.70	$267.70
Purchase #6	$104.73	12.570%	$117.8946	$117.89	$117.90	$117.90
Purchase #7	$94.81	5.768%	$100.2786	$100.28	$100.30	$100.30
7 purchase totals =	$936.95		$1,032.8961	$1,032.89	$1,032.85	$1,032.90