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	$161.52	10.403%	$178.3229	$178.32	$178.30	$178.30
Purchase #2	$11.92	5.793%	$12.6105	$12.61	$12.60	$12.60
Purchase #3	$165.74	5.502%	$174.859	$174.86	$174.85	$174.90
Purchase #4	$85.61	6.474%	$91.1524	$91.15	$91.15	$91.20
Purchase #5	$239.69	13.437%	$271.8971	$271.90	$271.90	$271.90
Purchase #6	$59.73	11.330%	$66.4974	$66.50	$66.50	$66.50
Purchase #7	$181.81	13.169%	$205.7526	$205.75	$205.75	$205.80
7 purchase totals =	$906.02		$1,001.0919	$1,001.09	$1,001.05	$1,001.20