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	$53.79	10.282%	$59.3207	$59.32	$59.30	$59.30
Purchase #2	$201.37	6.701%	$214.8638	$214.86	$214.85	$214.90
Purchase #3	$249.46	13.260%	$282.5384	$282.54	$282.55	$282.50
Purchase #4	$162.39	5.318%	$171.0259	$171.03	$171.05	$171.00
Purchase #5	$208.71	5.769%	$220.7505	$220.75	$220.75	$220.80
Purchase #6	$29.27	6.686%	$31.227	$31.23	$31.25	$31.20
Purchase #7	$161.53	11.782%	$180.5615	$180.56	$180.55	$180.60
7 purchase totals =	$1,066.52		$1,160.2878	$1,160.29	$1,160.30	$1,160.30