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	$135.44	4.508%	$141.5456	$141.55	$141.55	$141.50
Purchase #2	$5.42	3.403%	$5.6044	$5.60	$5.60	$5.60
Purchase #3	$220.91	11.593%	$246.5201	$246.52	$246.50	$246.50
Purchase #4	$65.46	11.483%	$72.9768	$72.98	$73.00	$73.00
Purchase #5	$101.56	9.532%	$111.2407	$111.24	$111.25	$111.20
Purchase #6	$58.47	4.530%	$61.1187	$61.12	$61.10	$61.10
Purchase #7	$87.88	10.171%	$96.8183	$96.82	$96.80	$96.80
7 purchase totals =	$675.14		$735.8246	$735.83	$735.80	$735.70