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	$194.61	5.725%	$205.7514	$205.75	$205.75	$205.80
Purchase #2	$150.43	11.166%	$167.227	$167.23	$167.25	$167.20
Purchase #3	$222.79	10.803%	$246.858	$246.86	$246.85	$246.90
Purchase #4	$30.30	10.848%	$33.5869	$33.59	$33.60	$33.60
Purchase #5	$184.62	5.346%	$194.4898	$194.49	$194.50	$194.50
Purchase #6	$63.97	12.849%	$72.1895	$72.19	$72.20	$72.20
Purchase #7	$57.32	3.113%	$59.1044	$59.10	$59.10	$59.10
7 purchase totals =	$904.04		$979.2070	$979.21	$979.25	$979.30