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	$172.63	11.812%	$193.0211	$193.02	$193.00	$193.00
Purchase #2	$97.72	13.681%	$111.0891	$111.09	$111.10	$111.10
Purchase #3	$222.94	10.308%	$245.9207	$245.92	$245.90	$245.90
Purchase #4	$152.60	10.658%	$168.8641	$168.86	$168.85	$168.90
Purchase #5	$235.26	9.631%	$257.9179	$257.92	$257.90	$257.90
Purchase #6	$6.92	5.840%	$7.3241	$7.32	$7.30	$7.30
Purchase #7	$197.57	9.144%	$215.6358	$215.64	$215.65	$215.60
7 purchase totals =	$1,085.64		$1,199.7728	$1,199.77	$1,199.70	$1,199.70