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	$238.89	5.293%	$251.5344	$251.53	$251.55	$251.50
Purchase #2	$242.47	10.185%	$267.1656	$267.17	$267.15	$267.20
Purchase #3	$37.56	7.571%	$40.4037	$40.40	$40.40	$40.40
Purchase #4	$240.91	8.238%	$260.7562	$260.76	$260.75	$260.80
Purchase #5	$101.69	7.285%	$109.0981	$109.10	$109.10	$109.10
Purchase #6	$59.94	9.345%	$65.5414	$65.54	$65.55	$65.50
Purchase #7	$196.25	7.642%	$211.2474	$211.25	$211.25	$211.20
7 purchase totals =	$1,117.71		$1,205.7468	$1,205.75	$1,205.75	$1,205.70