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	$79.57	12.517%	$89.5298	$89.53	$89.55	$89.50
Purchase #2	$224.98	5.816%	$238.0648	$238.06	$238.05	$238.10
Purchase #3	$119.48	12.739%	$134.7006	$134.70	$134.70	$134.70
Purchase #4	$199.73	8.315%	$216.3375	$216.34	$216.35	$216.30
Purchase #5	$166.68	3.457%	$172.4421	$172.44	$172.45	$172.40
Purchase #6	$245.25	4.615%	$256.5683	$256.57	$256.55	$256.60
Purchase #7	$58.53	4.160%	$60.9648	$60.96	$60.95	$61.00
7 purchase totals =	$1,094.22		$1,168.6079	$1,168.60	$1,168.60	$1,168.60