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	$130.40	13.183%	$147.5906	$147.59	$147.60	$147.60
Purchase #2	$66.67	6.538%	$71.0289	$71.03	$71.05	$71.00
Purchase #3	$194.36	9.839%	$213.4831	$213.48	$213.50	$213.50
Purchase #4	$47.31	10.773%	$52.4067	$52.41	$52.40	$52.40
Purchase #5	$50.30	5.119%	$52.8749	$52.87	$52.85	$52.90
Purchase #6	$127.55	10.526%	$140.9759	$140.98	$141.00	$141.00
Purchase #7	$5.95	10.150%	$6.5539	$6.55	$6.55	$6.60
7 purchase totals =	$622.54		$684.9140	$684.91	$684.95	$685.00