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	$136.79	3.463%	$141.527	$141.53	$141.55	$141.50
Purchase #2	$5.37	4.503%	$5.6118	$5.61	$5.60	$5.60
Purchase #3	$110.61	5.707%	$116.9225	$116.92	$116.90	$116.90
Purchase #4	$200.87	11.648%	$224.2673	$224.27	$224.25	$224.30
Purchase #5	$179.27	6.812%	$191.4819	$191.48	$191.50	$191.50
Purchase #6	$174.83	8.403%	$189.521	$189.52	$189.50	$189.50
Purchase #7	$80.79	12.612%	$90.9792	$90.98	$91.00	$91.00
7 purchase totals =	$888.53		$960.3107	$960.31	$960.30	$960.30