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	$223.72	6.586%	$238.4542	$238.45	$238.45	$238.50
Purchase #2	$170.69	11.815%	$190.857	$190.86	$190.85	$190.90
Purchase #3	$168.50	7.157%	$180.5595	$180.56	$180.55	$180.60
Purchase #4	$131.51	12.227%	$147.5897	$147.59	$147.60	$147.60
Purchase #5	$16.27	6.618%	$17.3467	$17.35	$17.35	$17.30
Purchase #6	$56.58	4.305%	$59.0158	$59.02	$59.00	$59.00
Purchase #7	$195.78	8.785%	$212.9793	$212.98	$213.00	$213.00
7 purchase totals =	$963.05		$1,046.8022	$1,046.81	$1,046.80	$1,046.90