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	$106.55	6.110%	$113.0602	$113.06	$113.05	$113.10
Purchase #2	$144.31	4.231%	$150.4158	$150.42	$150.40	$150.40
Purchase #3	$69.38	13.414%	$78.6866	$78.69	$78.70	$78.70
Purchase #4	$160.54	10.606%	$177.5669	$177.57	$177.55	$177.60
Purchase #5	$126.76	12.271%	$142.3147	$142.31	$142.30	$142.30
Purchase #6	$151.39	5.163%	$159.2063	$159.21	$159.20	$159.20
Purchase #7	$240.80	7.853%	$259.71	$259.71	$259.70	$259.70
7 purchase totals =	$999.73		$1,080.9605	$1,080.97	$1,080.90	$1,081.00