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	$57.26	4.252%	$59.6947	$59.69	$59.70	$59.70
Purchase #2	$104.48	13.679%	$118.7718	$118.77	$118.75	$118.80
Purchase #3	$134.92	11.824%	$150.8729	$150.87	$150.85	$150.90
Purchase #4	$184.35	11.338%	$205.2516	$205.25	$205.25	$205.30
Purchase #5	$116.92	12.124%	$131.0954	$131.10	$131.10	$131.10
Purchase #6	$61.58	13.334%	$69.7911	$69.79	$69.80	$69.80
Purchase #7	$100.34	11.495%	$111.8741	$111.87	$111.85	$111.90
7 purchase totals =	$759.85		$847.3516	$847.34	$847.30	$847.50