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	$198.48	7.249%	$212.8678	$212.87	$212.85	$212.90
Purchase #2	$100.60	4.574%	$105.2014	$105.20	$105.20	$105.20
Purchase #3	$222.89	9.358%	$243.748	$243.75	$243.75	$243.70
Purchase #4	$75.51	13.455%	$85.6699	$85.67	$85.65	$85.70
Purchase #5	$202.49	10.225%	$223.1946	$223.19	$223.20	$223.20
Purchase #6	$155.49	13.121%	$175.8918	$175.89	$175.90	$175.90
Purchase #7	$46.64	6.218%	$49.5401	$49.54	$49.55	$49.50
7 purchase totals =	$1,002.10		$1,096.1136	$1,096.11	$1,096.10	$1,096.10