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	$145.48	3.845%	$151.0737	$151.07	$151.05	$151.10
Purchase #2	$112.43	6.565%	$119.811	$119.81	$119.80	$119.80
Purchase #3	$176.27	12.549%	$198.3901	$198.39	$198.40	$198.40
Purchase #4	$149.97	12.624%	$168.9022	$168.90	$168.90	$168.90
Purchase #5	$223.95	5.160%	$235.5058	$235.51	$235.50	$235.50
Purchase #6	$73.47	6.612%	$78.3278	$78.33	$78.35	$78.30
Purchase #7	$172.76	4.437%	$180.4254	$180.43	$180.45	$180.40
7 purchase totals =	$1,054.33		$1,132.4360	$1,132.44	$1,132.45	$1,132.40