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	$53.33	13.516%	$60.5381	$60.54	$60.55	$60.50
Purchase #2	$222.88	6.698%	$237.8085	$237.81	$237.80	$237.80
Purchase #3	$164.52	4.196%	$171.4233	$171.42	$171.40	$171.40
Purchase #4	$150.89	13.629%	$171.4548	$171.45	$171.45	$171.50
Purchase #5	$157.65	5.700%	$166.6361	$166.64	$166.65	$166.60
Purchase #6	$232.84	9.864%	$255.8073	$255.81	$255.80	$255.80
Purchase #7	$79.89	6.581%	$85.1476	$85.15	$85.15	$85.10
7 purchase totals =	$1,062.00		$1,148.8157	$1,148.82	$1,148.80	$1,148.70