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	$138.90	11.436%	$154.7846	$154.78	$154.80	$154.80
Purchase #2	$35.77	7.133%	$38.3215	$38.32	$38.30	$38.30
Purchase #3	$79.67	11.434%	$88.7795	$88.78	$88.80	$88.80
Purchase #4	$54.88	7.765%	$59.1414	$59.14	$59.15	$59.10
Purchase #5	$172.63	4.802%	$180.9197	$180.92	$180.90	$180.90
Purchase #6	$15.76	11.483%	$17.5697	$17.57	$17.55	$17.60
Purchase #7	$167.72	11.833%	$187.5663	$187.57	$187.55	$187.60
7 purchase totals =	$665.33		$727.0827	$727.08	$727.05	$727.10