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	$164.41	9.628%	$180.2394	$180.24	$180.25	$180.20
Purchase #2	$16.70	10.683%	$18.4841	$18.48	$18.50	$18.50
Purchase #3	$91.73	5.706%	$96.9641	$96.96	$96.95	$97.00
Purchase #4	$78.55	13.512%	$89.1637	$89.16	$89.15	$89.20
Purchase #5	$80.66	8.233%	$87.3007	$87.30	$87.30	$87.30
Purchase #6	$170.90	8.694%	$185.758	$185.76	$185.75	$185.80
Purchase #7	$43.53	4.139%	$45.3317	$45.33	$45.35	$45.30
7 purchase totals =	$646.48		$703.2417	$703.23	$703.25	$703.30