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	$83.62	11.256%	$93.0323	$93.03	$93.05	$93.00
Purchase #2	$137.63	3.585%	$142.564	$142.56	$142.55	$142.60
Purchase #3	$142.54	7.676%	$153.4814	$153.48	$153.50	$153.50
Purchase #4	$82.88	4.433%	$86.5541	$86.55	$86.55	$86.60
Purchase #5	$147.39	3.339%	$152.3114	$152.31	$152.30	$152.30
Purchase #6	$91.59	4.762%	$95.9515	$95.95	$95.95	$96.00
Purchase #7	$139.74	9.443%	$152.9356	$152.94	$152.95	$152.90
7 purchase totals =	$825.39		$876.8303	$876.82	$876.85	$876.90