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	$218.71	9.769%	$240.0758	$240.08	$240.10	$240.10
Purchase #2	$145.48	4.511%	$152.0426	$152.04	$152.05	$152.00
Purchase #3	$83.78	6.348%	$89.0984	$89.10	$89.10	$89.10
Purchase #4	$245.55	4.192%	$255.8435	$255.84	$255.85	$255.80
Purchase #5	$69.70	3.147%	$71.8935	$71.89	$71.90	$71.90
Purchase #6	$87.81	3.271%	$90.6823	$90.68	$90.70	$90.70
Purchase #7	$231.81	7.753%	$249.7822	$249.78	$249.80	$249.80
7 purchase totals =	$1,082.84		$1,149.4183	$1,149.41	$1,149.50	$1,149.40