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	$121.98	10.242%	$134.4732	$134.47	$134.45	$134.50
Purchase #2	$247.32	3.195%	$255.2219	$255.22	$255.20	$255.20
Purchase #3	$221.54	3.612%	$229.542	$229.54	$229.55	$229.50
Purchase #4	$170.48	10.807%	$188.9038	$188.90	$188.90	$188.90
Purchase #5	$230.80	5.655%	$243.8517	$243.85	$243.85	$243.90
Purchase #6	$61.54	9.636%	$67.47	$67.47	$67.45	$67.50
Purchase #7	$214.46	5.218%	$225.6505	$225.65	$225.65	$225.70
7 purchase totals =	$1,268.12		$1,345.1131	$1,345.10	$1,345.05	$1,345.20