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	$73.58	7.326%	$78.9705	$78.97	$78.95	$79.00
Purchase #2	$9.79	4.287%	$10.2097	$10.21	$10.20	$10.20
Purchase #3	$89.90	4.756%	$94.1756	$94.18	$94.20	$94.20
Purchase #4	$92.90	9.593%	$101.8119	$101.81	$101.80	$101.80
Purchase #5	$50.78	12.558%	$57.157	$57.16	$57.15	$57.20
Purchase #6	$21.86	9.172%	$23.865	$23.87	$23.85	$23.90
Purchase #7	$85.76	5.856%	$90.7821	$90.78	$90.80	$90.80
7 purchase totals =	$424.57		$456.9718	$456.98	$456.95	$457.10