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	$140.80	4.437%	$147.0473	$147.05	$147.05	$147.00
Purchase #2	$23.49	8.776%	$25.5515	$25.55	$25.55	$25.60
Purchase #3	$103.30	9.812%	$113.4358	$113.44	$113.45	$113.40
Purchase #4	$99.90	5.539%	$105.4335	$105.43	$105.45	$105.40
Purchase #5	$98.31	13.697%	$111.7755	$111.78	$111.80	$111.80
Purchase #6	$136.75	13.825%	$155.6557	$155.66	$155.65	$155.70
Purchase #7	$167.71	4.571%	$175.376	$175.38	$175.40	$175.40
7 purchase totals =	$770.26		$834.2753	$834.29	$834.35	$834.30