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	$143.25	5.729%	$151.4568	$151.46	$151.45	$151.50
Purchase #2	$173.46	12.255%	$194.7175	$194.72	$194.70	$194.70
Purchase #3	$82.41	7.408%	$88.5149	$88.51	$88.50	$88.50
Purchase #4	$167.48	13.145%	$189.4952	$189.50	$189.50	$189.50
Purchase #5	$129.91	12.374%	$145.9851	$145.99	$146.00	$146.00
Purchase #6	$192.26	5.535%	$202.9016	$202.90	$202.90	$202.90
Purchase #7	$118.86	7.187%	$127.4025	$127.40	$127.40	$127.40
7 purchase totals =	$1,007.63		$1,100.4736	$1,100.48	$1,100.45	$1,100.50