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	$54.92	11.134%	$61.0348	$61.03	$61.05	$61.00
Purchase #2	$204.79	3.344%	$211.6382	$211.64	$211.65	$211.60
Purchase #3	$78.95	11.714%	$88.1982	$88.20	$88.20	$88.20
Purchase #4	$204.51	8.287%	$221.4577	$221.46	$221.45	$221.50
Purchase #5	$135.61	11.357%	$151.0112	$151.01	$151.00	$151.00
Purchase #6	$73.72	13.270%	$83.5026	$83.50	$83.50	$83.50
Purchase #7	$53.87	10.390%	$59.4671	$59.47	$59.45	$59.50
7 purchase totals =	$806.37		$876.3098	$876.31	$876.30	$876.30