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	$145.92	8.812%	$158.7785	$158.78	$158.80	$158.80
Purchase #2	$93.94	6.831%	$100.357	$100.36	$100.35	$100.40
Purchase #3	$5.65	3.300%	$5.8365	$5.84	$5.85	$5.80
Purchase #4	$233.44	4.664%	$244.3276	$244.33	$244.35	$244.30
Purchase #5	$153.60	7.866%	$165.6822	$165.68	$165.70	$165.70
Purchase #6	$85.59	5.711%	$90.478	$90.48	$90.50	$90.50
Purchase #7	$64.66	8.712%	$70.2932	$70.29	$70.30	$70.30
7 purchase totals =	$782.80		$835.7530	$835.76	$835.85	$835.80