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	$7.45	5.198%	$7.8373	$7.84	$7.85	$7.80
Purchase #2	$90.37	5.667%	$95.4913	$95.49	$95.50	$95.50
Purchase #3	$249.56	6.138%	$264.878	$264.88	$264.90	$264.90
Purchase #4	$61.59	3.666%	$63.8479	$63.85	$63.85	$63.80
Purchase #5	$137.50	13.226%	$155.6858	$155.69	$155.70	$155.70
Purchase #6	$113.35	5.680%	$119.7883	$119.79	$119.80	$119.80
Purchase #7	$28.48	3.227%	$29.399	$29.40	$29.40	$29.40
7 purchase totals =	$688.30		$736.9276	$736.94	$737.00	$736.90