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	$64.49	12.493%	$72.5467	$72.55	$72.55	$72.50
Purchase #2	$36.28	6.128%	$38.5032	$38.50	$38.50	$38.50
Purchase #3	$66.36	7.469%	$71.3164	$71.32	$71.30	$71.30
Purchase #4	$67.79	9.326%	$74.1121	$74.11	$74.10	$74.10
Purchase #5	$70.33	3.279%	$72.6361	$72.64	$72.65	$72.60
Purchase #6	$151.54	4.191%	$157.891	$157.89	$157.90	$157.90
Purchase #7	$197.25	5.672%	$208.438	$208.44	$208.45	$208.40
7 purchase totals =	$654.04		$695.4435	$695.45	$695.45	$695.30