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	$151.67	4.763%	$158.894	$158.89	$158.90	$158.90
Purchase #2	$76.30	12.125%	$85.5514	$85.55	$85.55	$85.60
Purchase #3	$41.61	12.133%	$46.6585	$46.66	$46.65	$46.70
Purchase #4	$154.90	4.756%	$162.267	$162.27	$162.25	$162.30
Purchase #5	$198.59	8.842%	$216.1493	$216.15	$216.15	$216.10
Purchase #6	$245.44	9.707%	$269.2649	$269.26	$269.25	$269.30
Purchase #7	$156.94	6.119%	$166.5432	$166.54	$166.55	$166.50
7 purchase totals =	$1,025.45		$1,105.3283	$1,105.32	$1,105.30	$1,105.40