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	$118.81	4.425%	$124.0673	$124.07	$124.05	$124.10
Purchase #2	$114.56	5.344%	$120.6821	$120.68	$120.70	$120.70
Purchase #3	$75.30	9.420%	$82.3933	$82.39	$82.40	$82.40
Purchase #4	$151.26	13.864%	$172.2307	$172.23	$172.25	$172.20
Purchase #5	$103.64	12.846%	$116.9536	$116.95	$116.95	$117.00
Purchase #6	$222.69	7.259%	$238.8551	$238.86	$238.85	$238.90
Purchase #7	$180.89	4.736%	$189.457	$189.46	$189.45	$189.50
7 purchase totals =	$967.15		$1,044.6391	$1,044.64	$1,044.65	$1,044.80