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	$111.26	6.582%	$118.5831	$118.58	$118.60	$118.60
Purchase #2	$104.34	13.809%	$118.7483	$118.75	$118.75	$118.70
Purchase #3	$90.69	12.499%	$102.0253	$102.03	$102.05	$102.00
Purchase #4	$189.45	3.845%	$196.7344	$196.73	$196.75	$196.70
Purchase #5	$75.53	13.159%	$85.469	$85.47	$85.45	$85.50
Purchase #6	$211.41	5.568%	$223.1813	$223.18	$223.20	$223.20
Purchase #7	$157.97	8.187%	$170.903	$170.90	$170.90	$170.90
7 purchase totals =	$940.65		$1,015.6444	$1,015.64	$1,015.70	$1,015.60