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	$72.53	8.737%	$78.8669	$78.87	$78.85	$78.90
Purchase #2	$12.27	7.208%	$13.1544	$13.15	$13.15	$13.20
Purchase #3	$54.36	13.840%	$61.8834	$61.88	$61.90	$61.90
Purchase #4	$110.50	11.273%	$122.9567	$122.96	$122.95	$123.00
Purchase #5	$218.76	8.834%	$238.0853	$238.09	$238.10	$238.10
Purchase #6	$192.69	6.399%	$205.0202	$205.02	$205.00	$205.00
Purchase #7	$29.30	13.537%	$33.2663	$33.27	$33.25	$33.30
7 purchase totals =	$690.41		$753.2332	$753.24	$753.20	$753.40