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	$247.36	3.707%	$256.5296	$256.53	$256.55	$256.50
Purchase #2	$208.97	8.767%	$227.2904	$227.29	$227.30	$227.30
Purchase #3	$173.32	7.249%	$185.884	$185.88	$185.90	$185.90
Purchase #4	$144.88	10.526%	$160.1301	$160.13	$160.15	$160.10
Purchase #5	$25.34	6.471%	$26.9798	$26.98	$27.00	$27.00
Purchase #6	$46.86	7.570%	$50.4073	$50.41	$50.40	$50.40
Purchase #7	$197.78	9.494%	$216.5572	$216.56	$216.55	$216.60
7 purchase totals =	$1,044.51		$1,123.7784	$1,123.78	$1,123.85	$1,123.80