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	$95.61	8.118%	$103.3716	$103.37	$103.35	$103.40
Purchase #2	$57.31	3.493%	$59.3118	$59.31	$59.30	$59.30
Purchase #3	$87.91	5.576%	$92.8119	$92.81	$92.80	$92.80
Purchase #4	$110.76	12.650%	$124.7711	$124.77	$124.75	$124.80
Purchase #5	$67.96	8.721%	$73.8868	$73.89	$73.90	$73.90
Purchase #6	$138.82	8.153%	$150.138	$150.14	$150.15	$150.10
Purchase #7	$193.98	3.565%	$200.8954	$200.90	$200.90	$200.90
7 purchase totals =	$752.35		$805.1866	$805.19	$805.15	$805.20