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	$24.37	4.702%	$25.5159	$25.52	$25.50	$25.50
Purchase #2	$100.63	5.183%	$105.8457	$105.85	$105.85	$105.80
Purchase #3	$81.31	3.148%	$83.8696	$83.87	$83.85	$83.90
Purchase #4	$137.48	11.489%	$153.2751	$153.28	$153.30	$153.30
Purchase #5	$89.27	11.838%	$99.8378	$99.84	$99.85	$99.80
Purchase #6	$202.65	12.738%	$228.4636	$228.46	$228.45	$228.50
Purchase #7	$57.82	11.669%	$64.567	$64.57	$64.55	$64.60
7 purchase totals =	$693.53		$761.3747	$761.39	$761.35	$761.40