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	$196.90	10.869%	$218.3011	$218.30	$218.30	$218.30
Purchase #2	$138.87	11.635%	$155.0275	$155.03	$155.05	$155.00
Purchase #3	$88.66	13.237%	$100.3959	$100.40	$100.40	$100.40
Purchase #4	$79.95	12.279%	$89.7671	$89.77	$89.75	$89.80
Purchase #5	$202.60	7.243%	$217.2743	$217.27	$217.25	$217.30
Purchase #6	$162.53	8.376%	$176.1435	$176.14	$176.15	$176.10
Purchase #7	$6.61	12.146%	$7.4129	$7.41	$7.40	$7.40
7 purchase totals =	$876.12		$964.3223	$964.32	$964.30	$964.30