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	$196.35	13.558%	$222.9711	$222.97	$222.95	$223.00
Purchase #2	$179.66	9.231%	$196.2444	$196.24	$196.25	$196.20
Purchase #3	$84.30	3.494%	$87.2454	$87.25	$87.25	$87.20
Purchase #4	$179.50	11.671%	$200.4494	$200.45	$200.45	$200.40
Purchase #5	$71.47	12.442%	$80.3623	$80.36	$80.35	$80.40
Purchase #6	$204.44	8.157%	$221.1162	$221.12	$221.10	$221.10
Purchase #7	$53.34	9.213%	$58.2542	$58.25	$58.25	$58.30
7 purchase totals =	$969.06		$1,066.6430	$1,066.64	$1,066.60	$1,066.60