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	$217.62	5.597%	$229.8002	$229.80	$229.80	$229.80
Purchase #2	$19.71	4.434%	$20.5839	$20.58	$20.60	$20.60
Purchase #3	$165.95	11.842%	$185.6018	$185.60	$185.60	$185.60
Purchase #4	$29.27	11.490%	$32.6331	$32.63	$32.65	$32.60
Purchase #5	$32.48	7.488%	$34.9121	$34.91	$34.90	$34.90
Purchase #6	$39.64	7.311%	$42.5381	$42.54	$42.55	$42.50
Purchase #7	$104.46	8.187%	$113.0121	$113.01	$113.00	$113.00
7 purchase totals =	$609.13		$659.0813	$659.07	$659.10	$659.00