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	$67.95	5.641%	$71.7831	$71.78	$71.80	$71.80
Purchase #2	$138.37	4.296%	$144.3144	$144.31	$144.30	$144.30
Purchase #3	$89.96	10.316%	$99.2403	$99.24	$99.25	$99.20
Purchase #4	$123.47	5.701%	$130.509	$130.51	$130.50	$130.50
Purchase #5	$244.28	4.584%	$255.4778	$255.48	$255.50	$255.50
Purchase #6	$211.75	9.594%	$232.0653	$232.07	$232.05	$232.10
Purchase #7	$104.53	13.692%	$118.8422	$118.84	$118.85	$118.80
7 purchase totals =	$980.31		$1,052.2321	$1,052.23	$1,052.25	$1,052.20