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	$153.82	10.129%	$169.4004	$169.40	$169.40	$169.40
Purchase #2	$205.55	3.777%	$213.3136	$213.31	$213.30	$213.30
Purchase #3	$101.98	9.283%	$111.4468	$111.45	$111.45	$111.40
Purchase #4	$102.92	3.357%	$106.375	$106.38	$106.40	$106.40
Purchase #5	$20.98	8.164%	$22.6928	$22.69	$22.70	$22.70
Purchase #6	$131.59	6.317%	$139.9025	$139.90	$139.90	$139.90
Purchase #7	$174.60	5.606%	$184.3881	$184.39	$184.40	$184.40
7 purchase totals =	$891.44		$947.5192	$947.52	$947.55	$947.50