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	$219.91	7.128%	$235.5852	$235.59	$235.60	$235.60
Purchase #2	$52.82	3.617%	$54.7305	$54.73	$54.75	$54.70
Purchase #3	$102.82	6.759%	$109.7696	$109.77	$109.75	$109.80
Purchase #4	$145.37	4.486%	$151.8913	$151.89	$151.90	$151.90
Purchase #5	$119.67	8.618%	$129.9832	$129.98	$130.00	$130.00
Purchase #6	$48.37	10.530%	$53.4634	$53.46	$53.45	$53.50
Purchase #7	$131.87	8.870%	$143.5669	$143.57	$143.55	$143.60
7 purchase totals =	$820.83		$878.9901	$878.99	$879.00	$879.10