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	$132.90	6.133%	$141.0508	$141.05	$141.05	$141.10
Purchase #2	$27.86	12.282%	$31.2818	$31.28	$31.30	$31.30
Purchase #3	$97.77	9.210%	$106.7746	$106.77	$106.75	$106.80
Purchase #4	$105.78	12.802%	$119.322	$119.32	$119.30	$119.30
Purchase #5	$137.96	13.178%	$156.1404	$156.14	$156.15	$156.10
Purchase #6	$162.28	3.599%	$168.1205	$168.12	$168.10	$168.10
Purchase #7	$35.55	6.455%	$37.8448	$37.84	$37.85	$37.80
7 purchase totals =	$700.10		$760.5349	$760.52	$760.50	$760.50