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	$140.96	8.614%	$153.1023	$153.10	$153.10	$153.10
Purchase #2	$114.79	7.471%	$123.366	$123.37	$123.35	$123.40
Purchase #3	$131.54	13.207%	$148.9125	$148.91	$148.90	$148.90
Purchase #4	$130.72	9.133%	$142.6587	$142.66	$142.65	$142.70
Purchase #5	$223.30	4.573%	$233.5115	$233.51	$233.50	$233.50
Purchase #6	$44.58	3.164%	$45.9905	$45.99	$46.00	$46.00
Purchase #7	$50.61	6.333%	$53.8151	$53.82	$53.80	$53.80
7 purchase totals =	$836.50		$901.3566	$901.36	$901.30	$901.40