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	$244.66	8.250%	$264.8445	$264.84	$264.85	$264.80
Purchase #2	$102.31	8.841%	$111.3552	$111.36	$111.35	$111.40
Purchase #3	$14.80	4.278%	$15.4331	$15.43	$15.45	$15.40
Purchase #4	$244.56	9.501%	$267.7956	$267.80	$267.80	$267.80
Purchase #5	$34.86	6.766%	$37.2186	$37.22	$37.20	$37.20
Purchase #6	$24.83	3.702%	$25.7492	$25.75	$25.75	$25.70
Purchase #7	$219.87	6.370%	$233.8757	$233.88	$233.90	$233.90
7 purchase totals =	$885.89		$956.2719	$956.28	$956.30	$956.20