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	$183.48	6.248%	$194.9438	$194.94	$194.95	$194.90
Purchase #2	$87.71	7.769%	$94.5242	$94.52	$94.50	$94.50
Purchase #3	$173.44	7.789%	$186.9492	$186.95	$186.95	$186.90
Purchase #4	$108.90	13.223%	$123.2998	$123.30	$123.30	$123.30
Purchase #5	$78.37	13.544%	$88.9844	$88.98	$89.00	$89.00
Purchase #6	$107.48	9.118%	$117.28	$117.28	$117.30	$117.30
Purchase #7	$240.78	5.660%	$254.4081	$254.41	$254.40	$254.40
7 purchase totals =	$980.16		$1,060.3895	$1,060.38	$1,060.40	$1,060.30