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	$144.75	5.133%	$152.18	$152.18	$152.20	$152.20
Purchase #2	$216.88	13.374%	$245.8855	$245.89	$245.90	$245.90
Purchase #3	$79.87	11.572%	$89.1126	$89.11	$89.10	$89.10
Purchase #4	$80.26	9.361%	$87.7731	$87.77	$87.75	$87.80
Purchase #5	$193.53	13.439%	$219.5385	$219.54	$219.55	$219.50
Purchase #6	$122.48	11.389%	$136.4292	$136.43	$136.45	$136.40
Purchase #7	$80.36	4.394%	$83.891	$83.89	$83.90	$83.90
7 purchase totals =	$918.13		$1,014.8099	$1,014.81	$1,014.85	$1,014.80