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	$138.69	6.690%	$147.9684	$147.97	$147.95	$148.00
Purchase #2	$230.97	3.358%	$238.726	$238.73	$238.75	$238.70
Purchase #3	$98.33	11.342%	$109.4826	$109.48	$109.50	$109.50
Purchase #4	$127.39	12.424%	$143.2169	$143.22	$143.20	$143.20
Purchase #5	$187.50	4.368%	$195.69	$195.69	$195.70	$195.70
Purchase #6	$117.43	6.696%	$125.2931	$125.29	$125.30	$125.30
Purchase #7	$153.79	12.134%	$172.4509	$172.45	$172.45	$172.50
7 purchase totals =	$1,054.10		$1,132.8279	$1,132.83	$1,132.85	$1,132.90