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	$58.60	11.343%	$65.247	$65.25	$65.25	$65.20
Purchase #2	$209.79	13.758%	$238.6529	$238.65	$238.65	$238.70
Purchase #3	$179.32	6.440%	$190.8682	$190.87	$190.85	$190.90
Purchase #4	$234.33	8.791%	$254.93	$254.93	$254.95	$254.90
Purchase #5	$174.91	3.195%	$180.4984	$180.50	$180.50	$180.50
Purchase #6	$248.98	6.626%	$265.4774	$265.48	$265.50	$265.50
Purchase #7	$40.90	5.669%	$43.2186	$43.22	$43.20	$43.20
7 purchase totals =	$1,146.83		$1,238.8925	$1,238.90	$1,238.90	$1,238.90