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	$59.47	8.532%	$64.544	$64.54	$64.55	$64.50
Purchase #2	$241.72	9.278%	$264.1468	$264.15	$264.15	$264.10
Purchase #3	$95.33	13.214%	$107.9269	$107.93	$107.95	$107.90
Purchase #4	$214.90	11.857%	$240.3807	$240.38	$240.40	$240.40
Purchase #5	$161.42	4.300%	$168.3611	$168.36	$168.35	$168.40
Purchase #6	$238.43	10.530%	$263.5367	$263.54	$263.55	$263.50
Purchase #7	$179.45	8.608%	$194.8971	$194.90	$194.90	$194.90
7 purchase totals =	$1,190.72		$1,303.7933	$1,303.80	$1,303.85	$1,303.70