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	$147.54	5.627%	$155.8421	$155.84	$155.85	$155.80
Purchase #2	$104.76	4.607%	$109.5863	$109.59	$109.60	$109.60
Purchase #3	$135.57	6.693%	$144.6437	$144.64	$144.65	$144.60
Purchase #4	$100.71	12.439%	$113.2373	$113.24	$113.25	$113.20
Purchase #5	$90.38	8.754%	$98.2919	$98.29	$98.30	$98.30
Purchase #6	$8.46	3.499%	$8.756	$8.76	$8.75	$8.80
Purchase #7	$130.43	6.662%	$139.1192	$139.12	$139.10	$139.10
7 purchase totals =	$717.85		$769.4765	$769.48	$769.50	$769.40