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	$172.72	3.122%	$178.1123	$178.11	$178.10	$178.10
Purchase #2	$31.98	10.583%	$35.3644	$35.36	$35.35	$35.40
Purchase #3	$156.47	6.573%	$166.7548	$166.75	$166.75	$166.80
Purchase #4	$185.83	5.541%	$196.1268	$196.13	$196.15	$196.10
Purchase #5	$131.68	7.293%	$141.2834	$141.28	$141.30	$141.30
Purchase #6	$188.74	6.165%	$200.3758	$200.38	$200.40	$200.40
Purchase #7	$54.32	13.326%	$61.5587	$61.56	$61.55	$61.60
7 purchase totals =	$921.74		$979.5762	$979.57	$979.60	$979.70