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	$33.27	12.158%	$37.315	$37.32	$37.30	$37.30
Purchase #2	$196.37	13.112%	$222.118	$222.12	$222.10	$222.10
Purchase #3	$212.55	11.482%	$236.955	$236.96	$236.95	$237.00
Purchase #4	$164.63	10.145%	$181.3317	$181.33	$181.35	$181.30
Purchase #5	$95.49	5.391%	$100.6379	$100.64	$100.65	$100.60
Purchase #6	$192.80	8.352%	$208.9027	$208.90	$208.90	$208.90
Purchase #7	$172.52	11.146%	$191.7491	$191.75	$191.75	$191.70
7 purchase totals =	$1,067.63		$1,179.0094	$1,179.02	$1,179.00	$1,178.90