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	$79.41	8.124%	$85.8613	$85.86	$85.85	$85.90
Purchase #2	$87.82	3.240%	$90.6654	$90.67	$90.65	$90.70
Purchase #3	$206.33	8.366%	$223.5916	$223.59	$223.60	$223.60
Purchase #4	$187.54	7.721%	$202.02	$202.02	$202.00	$202.00
Purchase #5	$187.53	11.479%	$209.0566	$209.06	$209.05	$209.10
Purchase #6	$146.34	4.774%	$153.3263	$153.33	$153.35	$153.30
Purchase #7	$208.45	12.163%	$233.8038	$233.80	$233.80	$233.80
7 purchase totals =	$1,103.42		$1,198.3250	$1,198.33	$1,198.30	$1,198.40