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	$148.95	13.154%	$168.5429	$168.54	$168.55	$168.50
Purchase #2	$20.85	7.376%	$22.3879	$22.39	$22.40	$22.40
Purchase #3	$214.46	13.574%	$243.5708	$243.57	$243.55	$243.60
Purchase #4	$128.90	9.492%	$141.1352	$141.14	$141.15	$141.10
Purchase #5	$36.94	12.644%	$41.6107	$41.61	$41.60	$41.60
Purchase #6	$141.27	4.383%	$147.4619	$147.46	$147.45	$147.50
Purchase #7	$70.69	12.729%	$79.6881	$79.69	$79.70	$79.70
7 purchase totals =	$762.06		$844.3975	$844.40	$844.40	$844.40