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	$107.39	6.204%	$114.0525	$114.05	$114.05	$114.10
Purchase #2	$213.25	10.457%	$235.5496	$235.55	$235.55	$235.50
Purchase #3	$131.35	10.753%	$145.4741	$145.47	$145.45	$145.50
Purchase #4	$201.34	9.249%	$219.9619	$219.96	$219.95	$220.00
Purchase #5	$35.44	13.856%	$40.3506	$40.35	$40.35	$40.40
Purchase #6	$89.76	7.620%	$96.5997	$96.60	$96.60	$96.60
Purchase #7	$78.27	9.767%	$85.9146	$85.91	$85.90	$85.90
7 purchase totals =	$856.80		$937.9030	$937.89	$937.85	$938.00