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	$123.43	8.582%	$134.0228	$134.02	$134.00	$134.00
Purchase #2	$71.46	13.450%	$81.0714	$81.07	$81.05	$81.10
Purchase #3	$201.83	13.749%	$229.5796	$229.58	$229.60	$229.60
Purchase #4	$142.61	5.782%	$150.8557	$150.86	$150.85	$150.90
Purchase #5	$233.46	9.700%	$256.1056	$256.11	$256.10	$256.10
Purchase #6	$247.39	4.634%	$258.8541	$258.85	$258.85	$258.90
Purchase #7	$102.78	11.807%	$114.9152	$114.92	$114.90	$114.90
7 purchase totals =	$1,122.96		$1,225.4044	$1,225.41	$1,225.35	$1,225.50