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	$186.32	5.333%	$196.2564	$196.26	$196.25	$196.30
Purchase #2	$148.57	6.785%	$158.6505	$158.65	$158.65	$158.70
Purchase #3	$67.88	13.671%	$77.1599	$77.16	$77.15	$77.20
Purchase #4	$111.37	10.656%	$123.2376	$123.24	$123.25	$123.20
Purchase #5	$95.27	8.139%	$103.024	$103.02	$103.00	$103.00
Purchase #6	$202.25	10.182%	$222.8431	$222.84	$222.85	$222.80
Purchase #7	$97.52	12.113%	$109.3326	$109.33	$109.35	$109.30
7 purchase totals =	$909.18		$990.5041	$990.50	$990.50	$990.50