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	$185.83	13.792%	$211.4597	$211.46	$211.45	$211.50
Purchase #2	$216.30	11.260%	$240.6554	$240.66	$240.65	$240.70
Purchase #3	$102.37	10.307%	$112.9213	$112.92	$112.90	$112.90
Purchase #4	$86.77	5.759%	$91.7671	$91.77	$91.75	$91.80
Purchase #5	$155.48	11.117%	$172.7647	$172.76	$172.75	$172.80
Purchase #6	$209.85	6.408%	$223.2972	$223.30	$223.30	$223.30
Purchase #7	$217.26	13.829%	$247.3049	$247.30	$247.30	$247.30
7 purchase totals =	$1,173.86		$1,300.1703	$1,300.17	$1,300.10	$1,300.30