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	$43.86	8.760%	$47.7021	$47.70	$47.70	$47.70
Purchase #2	$230.26	11.560%	$256.8781	$256.88	$256.90	$256.90
Purchase #3	$221.65	9.464%	$242.627	$242.63	$242.65	$242.60
Purchase #4	$188.61	6.229%	$200.3585	$200.36	$200.35	$200.40
Purchase #5	$19.56	10.638%	$21.6408	$21.64	$21.65	$21.60
Purchase #6	$114.63	11.259%	$127.5362	$127.54	$127.55	$127.50
Purchase #7	$115.45	9.154%	$126.0183	$126.02	$126.00	$126.00
7 purchase totals =	$934.02		$1,022.7610	$1,022.77	$1,022.80	$1,022.70