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	$59.89	7.708%	$64.5063	$64.51	$64.50	$64.50
Purchase #2	$84.63	7.249%	$90.7648	$90.76	$90.75	$90.80
Purchase #3	$130.47	11.576%	$145.5732	$145.57	$145.55	$145.60
Purchase #4	$250.70	3.456%	$259.3642	$259.36	$259.35	$259.40
Purchase #5	$127.95	13.803%	$145.6109	$145.61	$145.60	$145.60
Purchase #6	$246.41	3.825%	$255.8352	$255.84	$255.85	$255.80
Purchase #7	$152.28	6.531%	$162.2254	$162.23	$162.25	$162.20
7 purchase totals =	$1,052.33		$1,123.8800	$1,123.88	$1,123.85	$1,123.90