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	$87.55	13.611%	$99.4664	$99.47	$99.45	$99.50
Purchase #2	$52.39	5.187%	$55.1075	$55.11	$55.10	$55.10
Purchase #3	$216.34	13.660%	$245.892	$245.89	$245.90	$245.90
Purchase #4	$161.95	8.780%	$176.1692	$176.17	$176.15	$176.20
Purchase #5	$224.44	10.721%	$248.5022	$248.50	$248.50	$248.50
Purchase #6	$33.92	11.720%	$37.8954	$37.90	$37.90	$37.90
Purchase #7	$218.63	7.736%	$235.5432	$235.54	$235.55	$235.50
7 purchase totals =	$995.22		$1,098.5759	$1,098.58	$1,098.55	$1,098.60