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	$143.96	5.817%	$152.3342	$152.33	$152.35	$152.30
Purchase #2	$99.46	10.386%	$109.7899	$109.79	$109.80	$109.80
Purchase #3	$165.52	5.239%	$174.1916	$174.19	$174.20	$174.20
Purchase #4	$168.83	6.168%	$179.2434	$179.24	$179.25	$179.20
Purchase #5	$247.43	12.130%	$277.4433	$277.44	$277.45	$277.40
Purchase #6	$228.64	10.714%	$253.1365	$253.14	$253.15	$253.10
Purchase #7	$112.43	3.631%	$116.5123	$116.51	$116.50	$116.50
7 purchase totals =	$1,166.27		$1,262.6512	$1,262.64	$1,262.70	$1,262.50