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	$181.62	5.425%	$191.4729	$191.47	$191.45	$191.50
Purchase #2	$82.62	7.834%	$89.0925	$89.09	$89.10	$89.10
Purchase #3	$249.60	4.739%	$261.4285	$261.43	$261.45	$261.40
Purchase #4	$112.28	6.772%	$119.8836	$119.88	$119.90	$119.90
Purchase #5	$143.80	10.372%	$158.7149	$158.71	$158.70	$158.70
Purchase #6	$78.92	7.850%	$85.1152	$85.12	$85.10	$85.10
Purchase #7	$42.74	5.746%	$45.1958	$45.20	$45.20	$45.20
7 purchase totals =	$891.58		$950.9034	$950.90	$950.90	$950.90