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	$77.69	13.235%	$87.9723	$87.97	$87.95	$88.00
Purchase #2	$71.29	7.199%	$76.4222	$76.42	$76.40	$76.40
Purchase #3	$54.93	13.272%	$62.2203	$62.22	$62.20	$62.20
Purchase #4	$86.90	5.823%	$91.9602	$91.96	$91.95	$92.00
Purchase #5	$56.25	5.405%	$59.2903	$59.29	$59.30	$59.30
Purchase #6	$145.96	6.216%	$155.0329	$155.03	$155.05	$155.00
Purchase #7	$35.93	7.545%	$38.6409	$38.64	$38.65	$38.60
7 purchase totals =	$528.95		$571.5391	$571.53	$571.50	$571.50