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	$45.47	5.260%	$47.8617	$47.86	$47.85	$47.90
Purchase #2	$180.27	12.104%	$202.0899	$202.09	$202.10	$202.10
Purchase #3	$32.81	6.156%	$34.8298	$34.83	$34.85	$34.80
Purchase #4	$11.37	12.394%	$12.7792	$12.78	$12.80	$12.80
Purchase #5	$51.96	6.319%	$55.2434	$55.24	$55.25	$55.20
Purchase #6	$96.61	13.289%	$109.4485	$109.45	$109.45	$109.40
Purchase #7	$88.92	11.531%	$99.1734	$99.17	$99.15	$99.20
7 purchase totals =	$507.41		$561.4259	$561.42	$561.45	$561.40