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	$93.71	8.859%	$102.0118	$102.01	$102.00	$102.00
Purchase #2	$110.65	8.707%	$120.2843	$120.28	$120.30	$120.30
Purchase #3	$95.59	5.571%	$100.9153	$100.92	$100.90	$100.90
Purchase #4	$98.50	4.574%	$103.0054	$103.01	$103.00	$103.00
Purchase #5	$20.31	4.832%	$21.2914	$21.29	$21.30	$21.30
Purchase #6	$151.79	5.824%	$160.6302	$160.63	$160.65	$160.60
Purchase #7	$38.39	8.164%	$41.5242	$41.52	$41.50	$41.50
7 purchase totals =	$608.94		$649.6626	$649.66	$649.65	$649.60