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	$141.66	11.287%	$157.6492	$157.65	$157.65	$157.60
Purchase #2	$168.30	11.591%	$187.8077	$187.81	$187.80	$187.80
Purchase #3	$82.92	11.225%	$92.2278	$92.23	$92.25	$92.20
Purchase #4	$218.77	12.138%	$245.3243	$245.32	$245.30	$245.30
Purchase #5	$165.79	10.128%	$182.5812	$182.58	$182.60	$182.60
Purchase #6	$127.65	4.766%	$133.7338	$133.73	$133.75	$133.70
Purchase #7	$59.59	9.193%	$65.0681	$65.07	$65.05	$65.10
7 purchase totals =	$964.68		$1,064.3921	$1,064.39	$1,064.40	$1,064.30