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	$209.34	7.156%	$224.3204	$224.32	$224.30	$224.30
Purchase #2	$10.68	3.355%	$11.0383	$11.04	$11.05	$11.00
Purchase #3	$145.59	3.413%	$150.559	$150.56	$150.55	$150.60
Purchase #4	$137.98	13.194%	$156.1851	$156.19	$156.20	$156.20
Purchase #5	$200.92	11.179%	$223.3808	$223.38	$223.40	$223.40
Purchase #6	$35.51	5.292%	$37.3892	$37.39	$37.40	$37.40
Purchase #7	$119.47	4.306%	$124.6144	$124.61	$124.60	$124.60
7 purchase totals =	$859.49		$927.4872	$927.49	$927.50	$927.50