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	$181.81	5.260%	$191.3732	$191.37	$191.35	$191.40
Purchase #2	$143.51	12.387%	$161.2866	$161.29	$161.30	$161.30
Purchase #3	$72.53	8.429%	$78.6436	$78.64	$78.65	$78.60
Purchase #4	$113.97	5.592%	$120.3432	$120.34	$120.35	$120.30
Purchase #5	$71.58	12.361%	$80.428	$80.43	$80.45	$80.40
Purchase #6	$95.64	4.698%	$100.1332	$100.13	$100.15	$100.10
Purchase #7	$175.84	11.127%	$195.4057	$195.41	$195.40	$195.40
7 purchase totals =	$854.88		$927.6135	$927.61	$927.65	$927.50