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	$95.98	10.448%	$106.008	$106.01	$106.00	$106.00
Purchase #2	$118.44	9.852%	$130.1087	$130.11	$130.10	$130.10
Purchase #3	$174.39	6.408%	$185.5649	$185.56	$185.55	$185.60
Purchase #4	$56.59	5.528%	$59.7183	$59.72	$59.70	$59.70
Purchase #5	$144.85	4.667%	$151.6101	$151.61	$151.60	$151.60
Purchase #6	$118.51	9.620%	$129.9107	$129.91	$129.90	$129.90
Purchase #7	$174.48	7.217%	$187.0722	$187.07	$187.05	$187.10
7 purchase totals =	$883.24		$949.9929	$949.99	$949.90	$950.00