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	$205.82	5.348%	$216.8273	$216.83	$216.85	$216.80
Purchase #2	$56.30	9.864%	$61.8534	$61.85	$61.85	$61.90
Purchase #3	$95.96	5.714%	$101.4432	$101.44	$101.45	$101.40
Purchase #4	$241.37	3.623%	$250.1148	$250.11	$250.10	$250.10
Purchase #5	$106.39	7.514%	$114.3841	$114.38	$114.40	$114.40
Purchase #6	$181.25	8.567%	$196.7777	$196.78	$196.80	$196.80
Purchase #7	$231.62	11.436%	$258.1081	$258.11	$258.10	$258.10
7 purchase totals =	$1,118.71		$1,199.5086	$1,199.50	$1,199.55	$1,199.50