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	$84.81	5.374%	$89.3677	$89.37	$89.35	$89.40
Purchase #2	$224.97	6.838%	$240.3534	$240.35	$240.35	$240.40
Purchase #3	$29.59	13.798%	$33.6728	$33.67	$33.65	$33.70
Purchase #4	$175.43	11.647%	$195.8623	$195.86	$195.85	$195.90
Purchase #5	$116.63	8.553%	$126.6054	$126.61	$126.60	$126.60
Purchase #6	$231.85	4.772%	$242.9139	$242.91	$242.90	$242.90
Purchase #7	$87.42	4.607%	$91.4474	$91.45	$91.45	$91.40
7 purchase totals =	$950.70		$1,020.2229	$1,020.22	$1,020.15	$1,020.30