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	$172.38	5.790%	$182.3608	$182.36	$182.35	$182.40
Purchase #2	$72.76	13.317%	$82.4494	$82.45	$82.45	$82.40
Purchase #3	$142.29	12.299%	$159.7902	$159.79	$159.80	$159.80
Purchase #4	$50.87	10.627%	$56.276	$56.28	$56.30	$56.30
Purchase #5	$53.98	3.135%	$55.6723	$55.67	$55.65	$55.70
Purchase #6	$11.77	11.575%	$13.1324	$13.13	$13.15	$13.10
Purchase #7	$190.65	9.572%	$208.899	$208.90	$208.90	$208.90
7 purchase totals =	$694.70		$758.5801	$758.58	$758.60	$758.60