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	$160.43	4.190%	$167.152	$167.15	$167.15	$167.20
Purchase #2	$64.42	11.590%	$71.8863	$71.89	$71.90	$71.90
Purchase #3	$235.85	12.833%	$266.1166	$266.12	$266.10	$266.10
Purchase #4	$80.71	7.218%	$86.5356	$86.54	$86.55	$86.50
Purchase #5	$49.79	7.488%	$53.5183	$53.52	$53.50	$53.50
Purchase #6	$98.98	10.208%	$109.0839	$109.08	$109.10	$109.10
Purchase #7	$176.48	7.158%	$189.1124	$189.11	$189.10	$189.10
7 purchase totals =	$866.66		$943.4051	$943.41	$943.40	$943.40