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	$34.25	6.515%	$36.4814	$36.48	$36.50	$36.50
Purchase #2	$35.38	13.479%	$40.1489	$40.15	$40.15	$40.10
Purchase #3	$169.69	4.259%	$176.9171	$176.92	$176.90	$176.90
Purchase #4	$89.94	5.513%	$94.8984	$94.90	$94.90	$94.90
Purchase #5	$197.98	6.219%	$210.2924	$210.29	$210.30	$210.30
Purchase #6	$11.59	9.842%	$12.7307	$12.73	$12.75	$12.70
Purchase #7	$143.68	5.731%	$151.9143	$151.91	$151.90	$151.90
7 purchase totals =	$682.51		$723.3832	$723.38	$723.40	$723.30