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	$113.62	13.717%	$129.2053	$129.21	$129.20	$129.20
Purchase #2	$31.78	4.608%	$33.2444	$33.24	$33.25	$33.20
Purchase #3	$162.63	3.668%	$168.5953	$168.60	$168.60	$168.60
Purchase #4	$59.39	6.252%	$63.1031	$63.10	$63.10	$63.10
Purchase #5	$92.86	6.189%	$98.6071	$98.61	$98.60	$98.60
Purchase #6	$169.50	3.474%	$175.3884	$175.39	$175.40	$175.40
Purchase #7	$70.47	11.657%	$78.6847	$78.68	$78.70	$78.70
7 purchase totals =	$700.25		$746.8283	$746.83	$746.85	$746.80