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	$119.84	8.790%	$130.3739	$130.37	$130.35	$130.40
Purchase #2	$75.54	6.775%	$80.6578	$80.66	$80.65	$80.70
Purchase #3	$34.59	6.644%	$36.8882	$36.89	$36.90	$36.90
Purchase #4	$160.72	8.573%	$174.4985	$174.50	$174.50	$174.50
Purchase #5	$55.52	6.849%	$59.3226	$59.32	$59.30	$59.30
Purchase #6	$229.77	8.565%	$249.4498	$249.45	$249.45	$249.40
Purchase #7	$42.33	6.335%	$45.0116	$45.01	$45.00	$45.00
7 purchase totals =	$718.31		$776.2024	$776.20	$776.15	$776.20