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	$42.32	6.483%	$45.0636	$45.06	$45.05	$45.10
Purchase #2	$21.31	7.426%	$22.8925	$22.89	$22.90	$22.90
Purchase #3	$74.61	11.773%	$83.3938	$83.39	$83.40	$83.40
Purchase #4	$45.87	13.254%	$51.9496	$51.95	$51.95	$51.90
Purchase #5	$85.92	11.259%	$95.5937	$95.59	$95.60	$95.60
Purchase #6	$92.87	5.640%	$98.1079	$98.11	$98.10	$98.10
Purchase #7	$225.39	4.711%	$236.0081	$236.01	$236.00	$236.00
7 purchase totals =	$588.29		$633.0092	$633.00	$633.00	$633.00