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	$92.60	6.463%	$98.5847	$98.58	$98.60	$98.60
Purchase #2	$45.72	10.763%	$50.6408	$50.64	$50.65	$50.60
Purchase #3	$82.48	4.424%	$86.1289	$86.13	$86.15	$86.10
Purchase #4	$51.61	9.637%	$56.5837	$56.58	$56.60	$56.60
Purchase #5	$130.58	4.416%	$136.3464	$136.35	$136.35	$136.30
Purchase #6	$37.72	4.773%	$39.5204	$39.52	$39.50	$39.50
Purchase #7	$88.43	10.863%	$98.0362	$98.04	$98.05	$98.00
7 purchase totals =	$529.14		$565.8411	$565.84	$565.90	$565.70