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	$101.35	8.395%	$109.8583	$109.86	$109.85	$109.90
Purchase #2	$118.78	7.688%	$127.9118	$127.91	$127.90	$127.90
Purchase #3	$121.45	4.354%	$126.7379	$126.74	$126.75	$126.70
Purchase #4	$37.44	3.653%	$38.8077	$38.81	$38.80	$38.80
Purchase #5	$61.91	8.400%	$67.1104	$67.11	$67.10	$67.10
Purchase #6	$82.41	5.254%	$86.7398	$86.74	$86.75	$86.70
Purchase #7	$84.73	7.631%	$91.1957	$91.20	$91.20	$91.20
7 purchase totals =	$608.07		$648.3616	$648.37	$648.35	$648.30