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	$22.76	8.640%	$24.7265	$24.73	$24.75	$24.70
Purchase #2	$192.77	13.868%	$219.5033	$219.50	$219.50	$219.50
Purchase #3	$81.39	10.529%	$89.9596	$89.96	$89.95	$90.00
Purchase #4	$244.41	9.199%	$266.8933	$266.89	$266.90	$266.90
Purchase #5	$80.32	6.303%	$85.3826	$85.38	$85.40	$85.40
Purchase #6	$109.31	6.511%	$116.4272	$116.43	$116.45	$116.40
Purchase #7	$240.92	10.234%	$265.5758	$265.58	$265.60	$265.60
7 purchase totals =	$971.88		$1,068.4683	$1,068.47	$1,068.55	$1,068.50