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	$218.50	11.234%	$243.0463	$243.05	$243.05	$243.00
Purchase #2	$247.43	13.343%	$280.4446	$280.44	$280.45	$280.40
Purchase #3	$54.71	8.518%	$59.3702	$59.37	$59.35	$59.40
Purchase #4	$77.74	5.714%	$82.1821	$82.18	$82.20	$82.20
Purchase #5	$118.50	12.860%	$133.7391	$133.74	$133.75	$133.70
Purchase #6	$165.75	10.761%	$183.5864	$183.59	$183.60	$183.60
Purchase #7	$236.89	13.293%	$268.3798	$268.38	$268.40	$268.40
7 purchase totals =	$1,119.52		$1,250.7485	$1,250.75	$1,250.80	$1,250.70