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	$156.97	4.610%	$164.2063	$164.21	$164.20	$164.20
Purchase #2	$82.59	8.136%	$89.3095	$89.31	$89.30	$89.30
Purchase #3	$150.98	7.337%	$162.0574	$162.06	$162.05	$162.10
Purchase #4	$58.56	4.236%	$61.0406	$61.04	$61.05	$61.00
Purchase #5	$13.60	12.221%	$15.2621	$15.26	$15.25	$15.30
Purchase #6	$153.91	9.335%	$168.2775	$168.28	$168.30	$168.30
Purchase #7	$13.33	7.784%	$14.3676	$14.37	$14.35	$14.40
7 purchase totals =	$629.94		$674.5210	$674.53	$674.50	$674.60