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	$40.80	7.449%	$43.8392	$43.84	$43.85	$43.80
Purchase #2	$234.35	4.369%	$244.5888	$244.59	$244.60	$244.60
Purchase #3	$187.59	9.209%	$204.8652	$204.87	$204.85	$204.90
Purchase #4	$212.96	7.732%	$229.4261	$229.43	$229.45	$229.40
Purchase #5	$239.61	11.527%	$267.2298	$267.23	$267.25	$267.20
Purchase #6	$153.46	9.120%	$167.4556	$167.46	$167.45	$167.50
Purchase #7	$146.98	3.440%	$152.0361	$152.04	$152.05	$152.00
7 purchase totals =	$1,215.75		$1,309.4408	$1,309.46	$1,309.50	$1,309.40