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	$66.59	12.714%	$75.0563	$75.06	$75.05	$75.10
Purchase #2	$207.64	7.483%	$223.1777	$223.18	$223.20	$223.20
Purchase #3	$160.89	11.334%	$179.1253	$179.13	$179.15	$179.10
Purchase #4	$195.81	10.765%	$216.8889	$216.89	$216.90	$216.90
Purchase #5	$157.48	9.598%	$172.5949	$172.59	$172.60	$172.60
Purchase #6	$97.27	12.831%	$109.7507	$109.75	$109.75	$109.80
Purchase #7	$55.91	12.641%	$62.9776	$62.98	$63.00	$63.00
7 purchase totals =	$941.59		$1,039.5714	$1,039.58	$1,039.65	$1,039.70