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	$31.44	13.411%	$35.6564	$35.66	$35.65	$35.70
Purchase #2	$219.86	6.825%	$234.8654	$234.87	$234.85	$234.90
Purchase #3	$226.80	11.671%	$253.2698	$253.27	$253.25	$253.30
Purchase #4	$180.32	6.564%	$192.1562	$192.16	$192.15	$192.20
Purchase #5	$116.82	11.820%	$130.6281	$130.63	$130.65	$130.60
Purchase #6	$97.32	5.346%	$102.5227	$102.52	$102.50	$102.50
Purchase #7	$49.48	10.489%	$54.67	$54.67	$54.65	$54.70
7 purchase totals =	$922.04		$1,003.7686	$1,003.78	$1,003.70	$1,003.90