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	$100.70	4.870%	$105.6041	$105.60	$105.60	$105.60
Purchase #2	$204.77	9.163%	$223.5331	$223.53	$223.55	$223.50
Purchase #3	$50.65	4.844%	$53.1035	$53.10	$53.10	$53.10
Purchase #4	$166.27	8.112%	$179.7578	$179.76	$179.75	$179.80
Purchase #5	$109.63	4.445%	$114.5031	$114.50	$114.50	$114.50
Purchase #6	$62.80	10.215%	$69.215	$69.22	$69.20	$69.20
Purchase #7	$147.83	5.756%	$156.3391	$156.34	$156.35	$156.30
7 purchase totals =	$842.65		$902.0557	$902.05	$902.05	$902.00