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	$108.63	8.122%	$117.4529	$117.45	$117.45	$117.50
Purchase #2	$127.34	11.670%	$142.2006	$142.20	$142.20	$142.20
Purchase #3	$90.63	9.296%	$99.055	$99.06	$99.05	$99.10
Purchase #4	$175.91	7.694%	$189.4445	$189.44	$189.45	$189.40
Purchase #5	$239.33	12.632%	$269.5622	$269.56	$269.55	$269.60
Purchase #6	$134.53	6.821%	$143.7063	$143.71	$143.70	$143.70
Purchase #7	$180.46	11.359%	$200.9585	$200.96	$200.95	$201.00
7 purchase totals =	$1,056.83		$1,162.3800	$1,162.38	$1,162.35	$1,162.50