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	$220.86	13.378%	$250.4067	$250.41	$250.40	$250.40
Purchase #2	$87.45	5.684%	$92.4207	$92.42	$92.40	$92.40
Purchase #3	$70.76	4.397%	$73.8713	$73.87	$73.85	$73.90
Purchase #4	$179.71	9.474%	$196.7357	$196.74	$196.75	$196.70
Purchase #5	$246.81	13.473%	$280.0627	$280.06	$280.05	$280.10
Purchase #6	$54.94	12.777%	$61.9597	$61.96	$61.95	$62.00
Purchase #7	$175.41	9.402%	$191.902	$191.90	$191.90	$191.90
7 purchase totals =	$1,035.94		$1,147.3588	$1,147.36	$1,147.30	$1,147.40