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	$218.39	9.371%	$238.8553	$238.86	$238.85	$238.90
Purchase #2	$236.88	4.287%	$247.035	$247.04	$247.05	$247.00
Purchase #3	$231.81	9.852%	$254.6479	$254.65	$254.65	$254.60
Purchase #4	$145.37	4.474%	$151.8739	$151.87	$151.85	$151.90
Purchase #5	$59.33	10.303%	$65.4428	$65.44	$65.45	$65.40
Purchase #6	$24.88	3.861%	$25.8406	$25.84	$25.85	$25.80
Purchase #7	$35.99	6.442%	$38.3085	$38.31	$38.30	$38.30
7 purchase totals =	$952.65		$1,022.0040	$1,022.01	$1,022.00	$1,021.90