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	$33.45	6.549%	$35.6406	$35.64	$35.65	$35.60
Purchase #2	$238.25	10.502%	$263.271	$263.27	$263.25	$263.30
Purchase #3	$39.77	5.172%	$41.8269	$41.83	$41.85	$41.80
Purchase #4	$234.36	13.328%	$265.5955	$265.60	$265.60	$265.60
Purchase #5	$109.47	10.634%	$121.111	$121.11	$121.10	$121.10
Purchase #6	$64.29	12.658%	$72.4278	$72.43	$72.45	$72.40
Purchase #7	$202.68	10.357%	$223.6716	$223.67	$223.65	$223.70
7 purchase totals =	$922.27		$1,023.5444	$1,023.55	$1,023.55	$1,023.50