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	$247.42	10.714%	$273.9286	$273.93	$273.95	$273.90
Purchase #2	$191.50	13.347%	$217.0595	$217.06	$217.05	$217.10
Purchase #3	$29.73	4.572%	$31.0893	$31.09	$31.10	$31.10
Purchase #4	$50.36	8.117%	$54.4477	$54.45	$54.45	$54.40
Purchase #5	$235.25	4.674%	$246.2456	$246.25	$246.25	$246.20
Purchase #6	$57.42	3.516%	$59.4389	$59.44	$59.45	$59.40
Purchase #7	$154.48	13.441%	$175.2437	$175.24	$175.25	$175.20
7 purchase totals =	$966.16		$1,057.4533	$1,057.46	$1,057.50	$1,057.30