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	$211.67	5.749%	$223.8389	$223.84	$223.85	$223.80
Purchase #2	$130.66	4.497%	$136.5358	$136.54	$136.55	$136.50
Purchase #3	$124.90	13.217%	$141.408	$141.41	$141.40	$141.40
Purchase #4	$84.95	12.498%	$95.5671	$95.57	$95.55	$95.60
Purchase #5	$182.34	6.433%	$194.0699	$194.07	$194.05	$194.10
Purchase #6	$150.89	9.832%	$165.7255	$165.73	$165.75	$165.70
Purchase #7	$118.40	12.242%	$132.8945	$132.89	$132.90	$132.90
7 purchase totals =	$1,003.81		$1,090.0397	$1,090.05	$1,090.05	$1,090.00