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	$31.72	11.126%	$35.2492	$35.25	$35.25	$35.20
Purchase #2	$177.36	11.512%	$197.7777	$197.78	$197.80	$197.80
Purchase #3	$94.25	6.511%	$100.3866	$100.39	$100.40	$100.40
Purchase #4	$118.92	3.642%	$123.2511	$123.25	$123.25	$123.30
Purchase #5	$171.32	13.581%	$194.587	$194.59	$194.60	$194.60
Purchase #6	$143.97	6.742%	$153.6765	$153.68	$153.70	$153.70
Purchase #7	$89.36	12.222%	$100.2816	$100.28	$100.30	$100.30
7 purchase totals =	$826.90		$905.2097	$905.22	$905.30	$905.30