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	$161.57	7.639%	$173.9123	$173.91	$173.90	$173.90
Purchase #2	$217.50	5.418%	$229.2842	$229.28	$229.30	$229.30
Purchase #3	$122.66	10.768%	$135.868	$135.87	$135.85	$135.90
Purchase #4	$212.29	5.784%	$224.5689	$224.57	$224.55	$224.60
Purchase #5	$94.89	3.357%	$98.0755	$98.08	$98.10	$98.10
Purchase #6	$196.82	10.528%	$217.5412	$217.54	$217.55	$217.50
Purchase #7	$86.28	3.862%	$89.6121	$89.61	$89.60	$89.60
7 purchase totals =	$1,092.01		$1,168.8622	$1,168.86	$1,168.85	$1,168.90