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	$152.57	5.385%	$160.7859	$160.79	$160.80	$160.80
Purchase #2	$159.47	8.263%	$172.647	$172.65	$172.65	$172.60
Purchase #3	$79.41	10.422%	$87.6861	$87.69	$87.70	$87.70
Purchase #4	$233.39	13.576%	$265.075	$265.08	$265.10	$265.10
Purchase #5	$89.50	11.622%	$99.9017	$99.90	$99.90	$99.90
Purchase #6	$182.73	5.220%	$192.2685	$192.27	$192.25	$192.30
Purchase #7	$190.27	7.141%	$203.8572	$203.86	$203.85	$203.90
7 purchase totals =	$1,087.34		$1,182.2214	$1,182.24	$1,182.25	$1,182.30