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	$152.76	13.309%	$173.0908	$173.09	$173.10	$173.10
Purchase #2	$73.67	6.700%	$78.6059	$78.61	$78.60	$78.60
Purchase #3	$190.38	10.237%	$209.8692	$209.87	$209.85	$209.90
Purchase #4	$48.90	12.524%	$55.0242	$55.02	$55.00	$55.00
Purchase #5	$105.36	12.274%	$118.2919	$118.29	$118.30	$118.30
Purchase #6	$227.56	5.690%	$240.5082	$240.51	$240.50	$240.50
Purchase #7	$200.67	12.857%	$226.4701	$226.47	$226.45	$226.50
7 purchase totals =	$999.30		$1,101.8603	$1,101.86	$1,101.80	$1,101.90