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	$188.46	3.737%	$195.5028	$195.50	$195.50	$195.50
Purchase #2	$49.32	5.355%	$51.9611	$51.96	$51.95	$52.00
Purchase #3	$29.25	6.135%	$31.0445	$31.04	$31.05	$31.00
Purchase #4	$77.67	9.861%	$85.329	$85.33	$85.35	$85.30
Purchase #5	$103.92	7.690%	$111.9114	$111.91	$111.90	$111.90
Purchase #6	$45.58	5.408%	$48.045	$48.05	$48.05	$48.00
Purchase #7	$145.59	4.429%	$152.0382	$152.04	$152.05	$152.00
7 purchase totals =	$639.79		$675.8320	$675.83	$675.85	$675.70