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	$167.92	11.480%	$187.1972	$187.20	$187.20	$187.20
Purchase #2	$165.77	9.712%	$181.8696	$181.87	$181.85	$181.90
Purchase #3	$244.92	3.852%	$254.3543	$254.35	$254.35	$254.40
Purchase #4	$82.28	8.793%	$89.5149	$89.51	$89.50	$89.50
Purchase #5	$166.87	11.842%	$186.6307	$186.63	$186.65	$186.60
Purchase #6	$110.68	3.426%	$114.4719	$114.47	$114.45	$114.50
Purchase #7	$20.38	10.571%	$22.5344	$22.53	$22.55	$22.50
7 purchase totals =	$958.82		$1,036.5730	$1,036.56	$1,036.55	$1,036.60