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	$136.97	6.734%	$146.1936	$146.19	$146.20	$146.20
Purchase #2	$19.38	10.108%	$21.3389	$21.34	$21.35	$21.30
Purchase #3	$123.99	3.754%	$128.6446	$128.64	$128.65	$128.60
Purchase #4	$84.76	4.843%	$88.8649	$88.86	$88.85	$88.90
Purchase #5	$211.69	4.447%	$221.1039	$221.10	$221.10	$221.10
Purchase #6	$200.41	11.160%	$222.7758	$222.78	$222.80	$222.80
Purchase #7	$130.75	10.558%	$144.5546	$144.55	$144.55	$144.60
7 purchase totals =	$907.95		$973.4763	$973.46	$973.50	$973.50