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	$225.33	4.163%	$234.7105	$234.71	$234.70	$234.70
Purchase #2	$185.33	6.744%	$197.8287	$197.83	$197.85	$197.80
Purchase #3	$104.40	6.830%	$111.5305	$111.53	$111.55	$111.50
Purchase #4	$52.94	3.384%	$54.7315	$54.73	$54.75	$54.70
Purchase #5	$40.47	12.782%	$45.6429	$45.64	$45.65	$45.60
Purchase #6	$73.44	10.182%	$80.9177	$80.92	$80.90	$80.90
Purchase #7	$17.54	5.216%	$18.4549	$18.45	$18.45	$18.50
7 purchase totals =	$699.45		$743.8167	$743.81	$743.85	$743.70