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	$65.77	8.131%	$71.1178	$71.12	$71.10	$71.10
Purchase #2	$18.48	10.406%	$20.403	$20.40	$20.40	$20.40
Purchase #3	$170.39	11.380%	$189.7804	$189.78	$189.80	$189.80
Purchase #4	$96.64	4.842%	$101.3193	$101.32	$101.30	$101.30
Purchase #5	$68.64	13.342%	$77.7979	$77.80	$77.80	$77.80
Purchase #6	$15.38	6.345%	$16.3559	$16.36	$16.35	$16.40
Purchase #7	$13.89	11.802%	$15.5293	$15.53	$15.55	$15.50
7 purchase totals =	$449.19		$492.3036	$492.31	$492.30	$492.30