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	$98.44	11.633%	$109.8915	$109.89	$109.90	$109.90
Purchase #2	$24.72	4.473%	$25.8257	$25.83	$25.85	$25.80
Purchase #3	$139.39	5.479%	$147.0272	$147.03	$147.05	$147.00
Purchase #4	$130.82	6.338%	$139.1114	$139.11	$139.10	$139.10
Purchase #5	$159.89	8.180%	$172.969	$172.97	$172.95	$173.00
Purchase #6	$38.68	3.506%	$40.0361	$40.04	$40.05	$40.00
Purchase #7	$81.55	4.809%	$85.4717	$85.47	$85.45	$85.50
7 purchase totals =	$673.49		$720.3326	$720.34	$720.35	$720.30