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	$153.35	12.736%	$172.8807	$172.88	$172.90	$172.90
Purchase #2	$131.75	8.704%	$143.2175	$143.22	$143.20	$143.20
Purchase #3	$183.45	3.812%	$190.4431	$190.44	$190.45	$190.40
Purchase #4	$186.30	3.404%	$192.6417	$192.64	$192.65	$192.60
Purchase #5	$139.47	8.391%	$151.1729	$151.17	$151.15	$151.20
Purchase #6	$123.43	7.738%	$132.981	$132.98	$133.00	$133.00
Purchase #7	$73.34	9.476%	$80.2897	$80.29	$80.30	$80.30
7 purchase totals =	$991.09		$1,063.6266	$1,063.62	$1,063.65	$1,063.60