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	$127.74	11.480%	$142.4046	$142.40	$142.40	$142.40
Purchase #2	$217.82	7.831%	$234.8775	$234.88	$234.90	$234.90
Purchase #3	$17.37	6.201%	$18.4471	$18.45	$18.45	$18.40
Purchase #4	$167.50	6.820%	$178.9235	$178.92	$178.90	$178.90
Purchase #5	$175.35	11.791%	$196.0255	$196.03	$196.05	$196.00
Purchase #6	$105.38	9.488%	$115.3785	$115.38	$115.40	$115.40
Purchase #7	$82.89	6.672%	$88.4204	$88.42	$88.40	$88.40
7 purchase totals =	$894.05		$974.4771	$974.48	$974.50	$974.40