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	$45.41	11.645%	$50.698	$50.70	$50.70	$50.70
Purchase #2	$72.37	5.343%	$76.2367	$76.24	$76.25	$76.20
Purchase #3	$178.96	7.497%	$192.3766	$192.38	$192.40	$192.40
Purchase #4	$123.61	10.434%	$136.5075	$136.51	$136.50	$136.50
Purchase #5	$187.62	13.404%	$212.7686	$212.77	$212.75	$212.80
Purchase #6	$89.48	6.648%	$95.4286	$95.43	$95.45	$95.40
Purchase #7	$89.88	5.131%	$94.4917	$94.49	$94.50	$94.50
7 purchase totals =	$787.33		$858.5077	$858.52	$858.55	$858.50