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	$136.74	3.812%	$141.9525	$141.95	$141.95	$142.00
Purchase #2	$37.85	13.473%	$42.9495	$42.95	$42.95	$42.90
Purchase #3	$160.89	13.637%	$182.8306	$182.83	$182.85	$182.80
Purchase #4	$153.26	10.221%	$168.9247	$168.92	$168.90	$168.90
Purchase #5	$71.74	3.719%	$74.408	$74.41	$74.40	$74.40
Purchase #6	$152.91	6.224%	$162.4271	$162.43	$162.45	$162.40
Purchase #7	$168.36	10.838%	$186.6069	$186.61	$186.60	$186.60
7 purchase totals =	$881.75		$960.0993	$960.10	$960.10	$960.00