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	$246.34	5.378%	$259.5882	$259.59	$259.60	$259.60
Purchase #2	$194.53	4.271%	$202.8384	$202.84	$202.85	$202.80
Purchase #3	$46.76	8.516%	$50.7421	$50.74	$50.75	$50.70
Purchase #4	$141.59	12.666%	$159.5238	$159.52	$159.50	$159.50
Purchase #5	$101.41	11.752%	$113.3277	$113.33	$113.35	$113.30
Purchase #6	$145.68	3.229%	$150.384	$150.38	$150.40	$150.40
Purchase #7	$70.27	11.449%	$78.3152	$78.32	$78.30	$78.30
7 purchase totals =	$946.58		$1,014.7194	$1,014.72	$1,014.75	$1,014.60