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	$198.92	6.511%	$211.8717	$211.87	$211.85	$211.90
Purchase #2	$100.78	10.230%	$111.0898	$111.09	$111.10	$111.10
Purchase #3	$66.74	12.181%	$74.8696	$74.87	$74.85	$74.90
Purchase #4	$163.35	3.190%	$168.5609	$168.56	$168.55	$168.60
Purchase #5	$139.25	12.631%	$156.8387	$156.84	$156.85	$156.80
Purchase #6	$85.27	3.282%	$88.0686	$88.07	$88.05	$88.10
Purchase #7	$170.87	11.347%	$190.2586	$190.26	$190.25	$190.30
7 purchase totals =	$925.18		$1,001.5579	$1,001.56	$1,001.50	$1,001.70