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	$167.28	12.488%	$188.1699	$188.17	$188.15	$188.20
Purchase #2	$196.96	11.485%	$219.5809	$219.58	$219.60	$219.60
Purchase #3	$213.69	11.559%	$238.3904	$238.39	$238.40	$238.40
Purchase #4	$115.71	11.863%	$129.4367	$129.44	$129.45	$129.40
Purchase #5	$165.86	8.826%	$180.4988	$180.50	$180.50	$180.50
Purchase #6	$49.46	9.446%	$54.132	$54.13	$54.15	$54.10
Purchase #7	$32.32	10.849%	$35.8264	$35.83	$35.85	$35.80
7 purchase totals =	$941.28		$1,046.0351	$1,046.04	$1,046.10	$1,046.00