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	$99.53	3.577%	$103.0902	$103.09	$103.10	$103.10
Purchase #2	$57.32	11.763%	$64.0626	$64.06	$64.05	$64.10
Purchase #3	$58.49	6.103%	$62.0596	$62.06	$62.05	$62.10
Purchase #4	$185.42	5.214%	$195.0878	$195.09	$195.10	$195.10
Purchase #5	$199.39	9.189%	$217.7119	$217.71	$217.70	$217.70
Purchase #6	$198.30	5.653%	$209.5099	$209.51	$209.50	$209.50
Purchase #7	$105.56	11.820%	$118.0372	$118.04	$118.05	$118.00
7 purchase totals =	$904.01		$969.5592	$969.56	$969.55	$969.60