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	$196.81	10.599%	$217.6699	$217.67	$217.65	$217.70
Purchase #2	$185.51	13.125%	$209.8582	$209.86	$209.85	$209.90
Purchase #3	$25.83	4.558%	$27.0073	$27.01	$27.00	$27.00
Purchase #4	$146.81	10.670%	$162.4746	$162.47	$162.45	$162.50
Purchase #5	$31.84	6.576%	$33.9338	$33.93	$33.95	$33.90
Purchase #6	$11.55	10.474%	$12.7597	$12.76	$12.75	$12.80
Purchase #7	$77.44	6.616%	$82.5634	$82.56	$82.55	$82.60
7 purchase totals =	$675.79		$746.2669	$746.26	$746.20	$746.40