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	$202.62	12.192%	$227.3234	$227.32	$227.30	$227.30
Purchase #2	$225.37	13.158%	$255.0242	$255.02	$255.00	$255.00
Purchase #3	$107.51	10.424%	$118.7168	$118.72	$118.70	$118.70
Purchase #4	$100.97	4.112%	$105.1219	$105.12	$105.10	$105.10
Purchase #5	$186.42	10.793%	$206.5403	$206.54	$206.55	$206.50
Purchase #6	$224.61	3.427%	$232.3074	$232.31	$232.30	$232.30
Purchase #7	$51.99	7.279%	$55.7744	$55.77	$55.75	$55.80
7 purchase totals =	$1,099.49		$1,200.8084	$1,200.80	$1,200.70	$1,200.70