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	$122.68	9.563%	$134.4119	$134.41	$134.40	$134.40
Purchase #2	$55.50	6.863%	$59.309	$59.31	$59.30	$59.30
Purchase #3	$45.89	10.154%	$50.5497	$50.55	$50.55	$50.50
Purchase #4	$214.80	4.160%	$223.7357	$223.74	$223.75	$223.70
Purchase #5	$245.54	4.109%	$255.6292	$255.63	$255.65	$255.60
Purchase #6	$70.84	12.320%	$79.5675	$79.57	$79.55	$79.60
Purchase #7	$156.77	9.723%	$172.0127	$172.01	$172.00	$172.00
7 purchase totals =	$912.02		$975.2157	$975.22	$975.20	$975.10