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	$65.33	9.803%	$71.7343	$71.73	$71.75	$71.70
Purchase #2	$93.71	10.493%	$103.543	$103.54	$103.55	$103.50
Purchase #3	$56.43	8.268%	$61.0956	$61.10	$61.10	$61.10
Purchase #4	$101.88	13.643%	$115.7795	$115.78	$115.80	$115.80
Purchase #5	$32.89	13.857%	$37.4476	$37.45	$37.45	$37.40
Purchase #6	$170.81	12.465%	$192.1015	$192.10	$192.10	$192.10
Purchase #7	$74.78	7.365%	$80.2875	$80.29	$80.30	$80.30
7 purchase totals =	$595.83		$661.9890	$661.99	$662.05	$661.90