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	$148.96	5.687%	$157.4314	$157.43	$157.45	$157.40
Purchase #2	$92.67	6.467%	$98.663	$98.66	$98.65	$98.70
Purchase #3	$70.89	10.470%	$78.3122	$78.31	$78.30	$78.30
Purchase #4	$167.34	8.490%	$181.5472	$181.55	$181.55	$181.50
Purchase #5	$119.71	4.136%	$124.6612	$124.66	$124.65	$124.70
Purchase #6	$63.26	6.370%	$67.2897	$67.29	$67.30	$67.30
Purchase #7	$57.74	8.434%	$62.6098	$62.61	$62.60	$62.60
7 purchase totals =	$720.57		$770.5145	$770.51	$770.50	$770.50