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	$194.37	11.818%	$217.3406	$217.34	$217.35	$217.30
Purchase #2	$91.28	11.554%	$101.8265	$101.83	$101.85	$101.80
Purchase #3	$78.39	9.592%	$85.9092	$85.91	$85.90	$85.90
Purchase #4	$166.87	11.167%	$185.5044	$185.50	$185.50	$185.50
Purchase #5	$238.60	10.336%	$263.2617	$263.26	$263.25	$263.30
Purchase #6	$39.57	5.702%	$41.8263	$41.83	$41.85	$41.80
Purchase #7	$91.26	9.175%	$99.6331	$99.63	$99.65	$99.60
7 purchase totals =	$900.34		$995.3018	$995.30	$995.35	$995.20