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	$178.39	7.166%	$191.1734	$191.17	$191.15	$191.20
Purchase #2	$209.88	6.482%	$223.4844	$223.48	$223.50	$223.50
Purchase #3	$52.68	9.304%	$57.5813	$57.58	$57.60	$57.60
Purchase #4	$199.50	6.726%	$212.9184	$212.92	$212.90	$212.90
Purchase #5	$222.28	11.502%	$247.8466	$247.85	$247.85	$247.80
Purchase #6	$177.63	10.560%	$196.3877	$196.39	$196.40	$196.40
Purchase #7	$152.34	4.310%	$158.9059	$158.91	$158.90	$158.90
7 purchase totals =	$1,192.70		$1,288.2977	$1,288.30	$1,288.30	$1,288.30