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	$133.98	11.631%	$149.5632	$149.56	$149.55	$149.60
Purchase #2	$81.28	3.160%	$83.8484	$83.85	$83.85	$83.80
Purchase #3	$67.70	12.524%	$76.1787	$76.18	$76.20	$76.20
Purchase #4	$99.37	12.238%	$111.5309	$111.53	$111.55	$111.50
Purchase #5	$165.82	5.273%	$174.5637	$174.56	$174.55	$174.60
Purchase #6	$195.78	9.482%	$214.3439	$214.34	$214.35	$214.30
Purchase #7	$90.68	8.518%	$98.4041	$98.40	$98.40	$98.40
7 purchase totals =	$834.61		$908.4329	$908.42	$908.45	$908.40