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	$119.88	6.865%	$128.1098	$128.11	$128.10	$128.10
Purchase #2	$85.95	3.533%	$88.9866	$88.99	$89.00	$89.00
Purchase #3	$80.68	13.385%	$91.479	$91.48	$91.50	$91.50
Purchase #4	$167.31	11.145%	$185.9567	$185.96	$185.95	$186.00
Purchase #5	$162.94	3.620%	$168.8384	$168.84	$168.85	$168.80
Purchase #6	$148.79	5.813%	$157.4392	$157.44	$157.45	$157.40
Purchase #7	$82.35	10.215%	$90.7621	$90.76	$90.75	$90.80
7 purchase totals =	$847.90		$911.5718	$911.58	$911.60	$911.60