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	$151.62	10.705%	$167.8509	$167.85	$167.85	$167.90
Purchase #2	$244.64	9.311%	$267.4184	$267.42	$267.40	$267.40
Purchase #3	$79.48	4.166%	$82.7911	$82.79	$82.80	$82.80
Purchase #4	$52.26	4.470%	$54.596	$54.60	$54.60	$54.60
Purchase #5	$245.63	11.481%	$273.8308	$273.83	$273.85	$273.80
Purchase #6	$205.94	3.857%	$213.8831	$213.88	$213.90	$213.90
Purchase #7	$22.72	12.635%	$25.5907	$25.59	$25.60	$25.60
7 purchase totals =	$1,002.29		$1,085.9610	$1,085.96	$1,086.00	$1,086.00