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	$236.48	6.374%	$251.5532	$251.55	$251.55	$251.60
Purchase #2	$90.56	12.718%	$102.0774	$102.08	$102.10	$102.10
Purchase #3	$135.72	6.574%	$144.6422	$144.64	$144.65	$144.60
Purchase #4	$24.50	6.368%	$26.0602	$26.06	$26.05	$26.10
Purchase #5	$12.25	4.490%	$12.8	$12.80	$12.80	$12.80
Purchase #6	$94.39	6.585%	$100.6056	$100.61	$100.60	$100.60
Purchase #7	$57.38	3.684%	$59.4939	$59.49	$59.50	$59.50
7 purchase totals =	$651.28		$697.2325	$697.23	$697.25	$697.30