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	$148.81	11.479%	$165.8919	$165.89	$165.90	$165.90
Purchase #2	$64.33	8.134%	$69.5626	$69.56	$69.55	$69.60
Purchase #3	$178.75	11.719%	$199.6977	$199.70	$199.70	$199.70
Purchase #4	$76.96	4.660%	$80.5463	$80.55	$80.55	$80.50
Purchase #5	$168.50	9.795%	$185.0046	$185.00	$185.00	$185.00
Purchase #6	$156.94	4.574%	$164.1184	$164.12	$164.10	$164.10
Purchase #7	$165.42	13.718%	$188.1123	$188.11	$188.10	$188.10
7 purchase totals =	$959.71		$1,052.9338	$1,052.93	$1,052.90	$1,052.90