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	$127.35	10.653%	$140.9166	$140.92	$140.90	$140.90
Purchase #2	$113.87	5.285%	$119.888	$119.89	$119.90	$119.90
Purchase #3	$96.28	11.645%	$107.4918	$107.49	$107.50	$107.50
Purchase #4	$25.37	9.490%	$27.7776	$27.78	$27.80	$27.80
Purchase #5	$74.79	5.505%	$78.9072	$78.91	$78.90	$78.90
Purchase #6	$150.93	7.609%	$162.4143	$162.41	$162.40	$162.40
Purchase #7	$235.61	5.303%	$248.1044	$248.10	$248.10	$248.10
7 purchase totals =	$824.20		$885.4999	$885.50	$885.50	$885.50