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	$64.47	5.244%	$67.8508	$67.85	$67.85	$67.90
Purchase #2	$90.31	5.180%	$94.9881	$94.99	$95.00	$95.00
Purchase #3	$189.57	11.173%	$210.7507	$210.75	$210.75	$210.80
Purchase #4	$96.73	3.765%	$100.3719	$100.37	$100.35	$100.40
Purchase #5	$87.90	6.513%	$93.6249	$93.62	$93.60	$93.60
Purchase #6	$50.85	8.411%	$55.127	$55.13	$55.15	$55.10
Purchase #7	$92.38	7.814%	$99.5986	$99.60	$99.60	$99.60
7 purchase totals =	$672.21		$722.3120	$722.31	$722.30	$722.40