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	$54.54	8.641%	$59.2528	$59.25	$59.25	$59.30
Purchase #2	$152.79	9.371%	$167.108	$167.11	$167.10	$167.10
Purchase #3	$18.41	5.850%	$19.487	$19.49	$19.50	$19.50
Purchase #4	$166.30	13.206%	$188.2616	$188.26	$188.25	$188.30
Purchase #5	$163.54	7.176%	$175.2756	$175.28	$175.30	$175.30
Purchase #6	$248.78	13.719%	$282.9101	$282.91	$282.90	$282.90
Purchase #7	$220.72	8.488%	$239.4547	$239.45	$239.45	$239.50
7 purchase totals =	$1,025.08		$1,131.7498	$1,131.75	$1,131.75	$1,131.90