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	$103.89	10.306%	$114.5969	$114.60	$114.60	$114.60
Purchase #2	$134.60	13.128%	$152.2703	$152.27	$152.25	$152.30
Purchase #3	$233.30	12.426%	$262.2899	$262.29	$262.30	$262.30
Purchase #4	$245.84	7.801%	$265.018	$265.02	$265.00	$265.00
Purchase #5	$49.68	12.505%	$55.8925	$55.89	$55.90	$55.90
Purchase #6	$149.56	7.522%	$160.8099	$160.81	$160.80	$160.80
Purchase #7	$132.29	3.497%	$136.9162	$136.92	$136.90	$136.90
7 purchase totals =	$1,049.16		$1,147.7937	$1,147.80	$1,147.75	$1,147.80