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	$117.89	5.163%	$123.9767	$123.98	$124.00	$124.00
Purchase #2	$117.61	11.440%	$131.0646	$131.06	$131.05	$131.10
Purchase #3	$95.70	3.796%	$99.3328	$99.33	$99.35	$99.30
Purchase #4	$40.84	3.811%	$42.3964	$42.40	$42.40	$42.40
Purchase #5	$46.35	3.242%	$47.8527	$47.85	$47.85	$47.90
Purchase #6	$26.59	3.370%	$27.4861	$27.49	$27.50	$27.50
Purchase #7	$199.98	12.853%	$225.6834	$225.68	$225.70	$225.70
7 purchase totals =	$644.96		$697.7927	$697.79	$697.85	$697.90