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	$98.61	10.588%	$109.0508	$109.05	$109.05	$109.10
Purchase #2	$244.56	11.432%	$272.5181	$272.52	$272.50	$272.50
Purchase #3	$107.86	5.259%	$113.5324	$113.53	$113.55	$113.50
Purchase #4	$165.34	7.732%	$178.1241	$178.12	$178.10	$178.10
Purchase #5	$243.75	11.396%	$271.5278	$271.53	$271.55	$271.50
Purchase #6	$182.49	6.404%	$194.1767	$194.18	$194.20	$194.20
Purchase #7	$74.92	3.490%	$77.5347	$77.53	$77.55	$77.50
7 purchase totals =	$1,117.53		$1,216.4646	$1,216.46	$1,216.50	$1,216.40