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	$174.37	9.237%	$190.4766	$190.48	$190.50	$190.50
Purchase #2	$147.89	9.802%	$162.3862	$162.39	$162.40	$162.40
Purchase #3	$213.60	11.653%	$238.4908	$238.49	$238.50	$238.50
Purchase #4	$159.59	12.809%	$180.0319	$180.03	$180.05	$180.00
Purchase #5	$66.80	4.565%	$69.8494	$69.85	$69.85	$69.80
Purchase #6	$123.96	3.442%	$128.2267	$128.23	$128.25	$128.20
Purchase #7	$17.43	12.322%	$19.5777	$19.58	$19.60	$19.60
7 purchase totals =	$903.64		$989.0393	$989.05	$989.15	$989.00