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	$137.58	9.562%	$150.7354	$150.74	$150.75	$150.70
Purchase #2	$193.33	8.744%	$210.2348	$210.23	$210.25	$210.20
Purchase #3	$232.51	10.185%	$256.1911	$256.19	$256.20	$256.20
Purchase #4	$164.75	4.606%	$172.3384	$172.34	$172.35	$172.30
Purchase #5	$136.61	4.772%	$143.129	$143.13	$143.15	$143.10
Purchase #6	$70.59	11.857%	$78.9599	$78.96	$78.95	$79.00
Purchase #7	$239.61	4.714%	$250.9052	$250.91	$250.90	$250.90
7 purchase totals =	$1,174.98		$1,262.4938	$1,262.50	$1,262.55	$1,262.40