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	$188.33	5.814%	$199.2795	$199.28	$199.30	$199.30
Purchase #2	$74.49	11.843%	$83.3119	$83.31	$83.30	$83.30
Purchase #3	$184.85	3.151%	$190.6746	$190.67	$190.65	$190.70
Purchase #4	$145.92	13.550%	$165.6922	$165.69	$165.70	$165.70
Purchase #5	$150.71	13.743%	$171.4221	$171.42	$171.40	$171.40
Purchase #6	$167.69	10.115%	$184.6518	$184.65	$184.65	$184.70
Purchase #7	$41.72	13.644%	$47.4123	$47.41	$47.40	$47.40
7 purchase totals =	$953.71		$1,042.4444	$1,042.43	$1,042.40	$1,042.50