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	$110.80	11.600%	$123.6528	$123.65	$123.65	$123.70
Purchase #2	$158.40	11.289%	$176.2818	$176.28	$176.30	$176.30
Purchase #3	$144.32	6.328%	$153.4526	$153.45	$153.45	$153.50
Purchase #4	$123.26	13.239%	$139.5784	$139.58	$139.60	$139.60
Purchase #5	$191.34	9.824%	$210.1372	$210.14	$210.15	$210.10
Purchase #6	$63.76	5.862%	$67.4976	$67.50	$67.50	$67.50
Purchase #7	$147.39	12.349%	$165.5912	$165.59	$165.60	$165.60
7 purchase totals =	$939.27		$1,036.1916	$1,036.19	$1,036.25	$1,036.30