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	$32.76	3.345%	$33.8558	$33.86	$33.85	$33.90
Purchase #2	$19.60	3.136%	$20.2147	$20.21	$20.20	$20.20
Purchase #3	$220.66	3.637%	$228.6854	$228.69	$228.70	$228.70
Purchase #4	$73.89	6.314%	$78.5554	$78.56	$78.55	$78.60
Purchase #5	$109.34	4.539%	$114.3029	$114.30	$114.30	$114.30
Purchase #6	$74.34	10.756%	$82.336	$82.34	$82.35	$82.30
Purchase #7	$197.37	8.753%	$214.6458	$214.65	$214.65	$214.60
7 purchase totals =	$727.96		$772.5960	$772.61	$772.60	$772.60