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	$49.90	12.309%	$56.0422	$56.04	$56.05	$56.00
Purchase #2	$142.37	6.738%	$151.9629	$151.96	$151.95	$152.00
Purchase #3	$100.55	4.443%	$105.0174	$105.02	$105.00	$105.00
Purchase #4	$60.38	11.411%	$67.27	$67.27	$67.25	$67.30
Purchase #5	$99.80	13.575%	$113.3479	$113.35	$113.35	$113.30
Purchase #6	$25.78	11.472%	$28.7375	$28.74	$28.75	$28.70
Purchase #7	$168.80	12.329%	$189.6114	$189.61	$189.60	$189.60
7 purchase totals =	$647.58		$711.9893	$711.99	$711.95	$711.90