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	$83.46	9.735%	$91.5848	$91.58	$91.60	$91.60
Purchase #2	$18.56	6.867%	$19.8345	$19.83	$19.85	$19.80
Purchase #3	$148.27	9.565%	$162.452	$162.45	$162.45	$162.50
Purchase #4	$108.47	8.388%	$117.5685	$117.57	$117.55	$117.60
Purchase #5	$188.40	4.431%	$196.748	$196.75	$196.75	$196.70
Purchase #6	$66.60	8.651%	$72.3616	$72.36	$72.35	$72.40
Purchase #7	$167.64	7.691%	$180.5332	$180.53	$180.55	$180.50
7 purchase totals =	$781.40		$841.0826	$841.07	$841.10	$841.10