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	$195.83	7.669%	$210.8482	$210.85	$210.85	$210.80
Purchase #2	$177.49	10.593%	$196.2915	$196.29	$196.30	$196.30
Purchase #3	$104.69	3.280%	$108.1238	$108.12	$108.10	$108.10
Purchase #4	$135.26	6.863%	$144.5429	$144.54	$144.55	$144.50
Purchase #5	$18.80	8.706%	$20.4367	$20.44	$20.45	$20.40
Purchase #6	$180.51	8.463%	$195.7866	$195.79	$195.80	$195.80
Purchase #7	$35.27	5.697%	$37.2793	$37.28	$37.30	$37.30
7 purchase totals =	$847.85		$913.3090	$913.31	$913.35	$913.20