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	$67.53	5.263%	$71.0841	$71.08	$71.10	$71.10
Purchase #2	$135.48	11.839%	$151.5195	$151.52	$151.50	$151.50
Purchase #3	$220.92	7.152%	$236.7202	$236.72	$236.70	$236.70
Purchase #4	$217.78	11.257%	$242.2955	$242.30	$242.30	$242.30
Purchase #5	$50.42	12.423%	$56.6837	$56.68	$56.70	$56.70
Purchase #6	$237.34	13.140%	$268.5265	$268.53	$268.55	$268.50
Purchase #7	$33.91	13.432%	$38.4648	$38.46	$38.45	$38.50
7 purchase totals =	$963.38		$1,065.2943	$1,065.29	$1,065.30	$1,065.30