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	$158.30	3.779%	$164.2822	$164.28	$164.30	$164.30
Purchase #2	$167.88	10.598%	$185.6719	$185.67	$185.65	$185.70
Purchase #3	$31.57	8.556%	$34.2711	$34.27	$34.25	$34.30
Purchase #4	$172.56	10.164%	$190.099	$190.10	$190.10	$190.10
Purchase #5	$192.47	11.238%	$214.0998	$214.10	$214.10	$214.10
Purchase #6	$224.55	10.279%	$247.6315	$247.63	$247.65	$247.60
Purchase #7	$28.32	9.765%	$31.0854	$31.09	$31.10	$31.10
7 purchase totals =	$975.65		$1,067.1409	$1,067.14	$1,067.15	$1,067.20