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	$159.71	9.280%	$174.5311	$174.53	$174.55	$174.50
Purchase #2	$87.98	7.373%	$94.4668	$94.47	$94.45	$94.50
Purchase #3	$194.39	11.443%	$216.634	$216.63	$216.65	$216.60
Purchase #4	$147.54	13.178%	$166.9828	$166.98	$167.00	$167.00
Purchase #5	$54.85	4.271%	$57.1926	$57.19	$57.20	$57.20
Purchase #6	$126.71	9.650%	$138.9375	$138.94	$138.95	$138.90
Purchase #7	$233.56	9.364%	$255.4306	$255.43	$255.45	$255.40
7 purchase totals =	$1,004.74		$1,104.1754	$1,104.17	$1,104.25	$1,104.10