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	$82.89	12.172%	$92.9794	$92.98	$93.00	$93.00
Purchase #2	$147.52	13.125%	$166.882	$166.88	$166.90	$166.90
Purchase #3	$136.43	4.211%	$142.1751	$142.18	$142.20	$142.20
Purchase #4	$218.78	11.746%	$244.4779	$244.48	$244.50	$244.50
Purchase #5	$171.35	11.620%	$191.2609	$191.26	$191.25	$191.30
Purchase #6	$35.47	9.279%	$38.7613	$38.76	$38.75	$38.80
Purchase #7	$75.33	3.740%	$78.1473	$78.15	$78.15	$78.10
7 purchase totals =	$867.77		$954.6839	$954.69	$954.75	$954.80