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	$133.97	7.537%	$144.0673	$144.07	$144.05	$144.10
Purchase #2	$67.68	3.831%	$70.2728	$70.27	$70.25	$70.30
Purchase #3	$142.63	12.379%	$160.2862	$160.29	$160.30	$160.30
Purchase #4	$199.38	11.674%	$222.6556	$222.66	$222.65	$222.70
Purchase #5	$88.94	12.406%	$99.9739	$99.97	$99.95	$100.00
Purchase #6	$237.29	5.450%	$250.2223	$250.22	$250.20	$250.20
Purchase #7	$70.89	6.497%	$75.4957	$75.50	$75.50	$75.50
7 purchase totals =	$940.78		$1,022.9738	$1,022.98	$1,022.90	$1,023.10