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	$141.77	9.310%	$154.9688	$154.97	$154.95	$155.00
Purchase #2	$104.67	6.188%	$111.147	$111.15	$111.15	$111.10
Purchase #3	$247.63	6.152%	$262.8642	$262.86	$262.85	$262.90
Purchase #4	$42.79	7.834%	$46.1422	$46.14	$46.15	$46.10
Purchase #5	$89.39	8.853%	$97.3037	$97.30	$97.30	$97.30
Purchase #6	$9.35	5.442%	$9.8588	$9.86	$9.85	$9.90
Purchase #7	$83.83	8.446%	$90.9103	$90.91	$90.90	$90.90
7 purchase totals =	$719.43		$773.1950	$773.19	$773.15	$773.20