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	$94.41	6.536%	$100.5806	$100.58	$100.60	$100.60
Purchase #2	$143.67	6.370%	$152.8218	$152.82	$152.80	$152.80
Purchase #3	$190.98	12.800%	$215.4254	$215.43	$215.45	$215.40
Purchase #4	$124.58	10.627%	$137.8191	$137.82	$137.80	$137.80
Purchase #5	$160.54	5.738%	$169.7518	$169.75	$169.75	$169.80
Purchase #6	$10.53	6.377%	$11.2015	$11.20	$11.20	$11.20
Purchase #7	$200.72	11.220%	$223.2408	$223.24	$223.25	$223.20
7 purchase totals =	$925.43		$1,010.8410	$1,010.84	$1,010.85	$1,010.80