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	$156.92	5.465%	$165.4957	$165.50	$165.50	$165.50
Purchase #2	$205.92	7.864%	$222.1135	$222.11	$222.10	$222.10
Purchase #3	$7.47	7.156%	$8.0046	$8.00	$8.00	$8.00
Purchase #4	$125.88	9.358%	$137.6599	$137.66	$137.65	$137.70
Purchase #5	$131.57	5.739%	$139.1208	$139.12	$139.10	$139.10
Purchase #6	$227.28	7.324%	$243.926	$243.93	$243.95	$243.90
Purchase #7	$220.37	6.222%	$234.0814	$234.08	$234.10	$234.10
7 purchase totals =	$1,075.41		$1,150.4019	$1,150.40	$1,150.40	$1,150.40