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	$21.50	9.206%	$23.4793	$23.48	$23.50	$23.50
Purchase #2	$184.59	6.673%	$196.9077	$196.91	$196.90	$196.90
Purchase #3	$212.47	6.132%	$225.4987	$225.50	$225.50	$225.50
Purchase #4	$30.83	9.449%	$33.7431	$33.74	$33.75	$33.70
Purchase #5	$225.61	8.512%	$244.8139	$244.81	$244.80	$244.80
Purchase #6	$85.74	4.206%	$89.3462	$89.35	$89.35	$89.30
Purchase #7	$197.86	10.769%	$219.1675	$219.17	$219.15	$219.20
7 purchase totals =	$958.60		$1,032.9564	$1,032.96	$1,032.95	$1,032.90