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	$130.63	9.803%	$143.4357	$143.44	$143.45	$143.40
Purchase #2	$25.98	9.411%	$28.425	$28.43	$28.45	$28.40
Purchase #3	$200.71	5.799%	$212.3492	$212.35	$212.35	$212.30
Purchase #4	$92.98	13.241%	$105.2915	$105.29	$105.30	$105.30
Purchase #5	$146.88	9.564%	$160.9276	$160.93	$160.95	$160.90
Purchase #6	$241.81	11.852%	$270.4693	$270.47	$270.45	$270.50
Purchase #7	$78.48	5.315%	$82.6512	$82.65	$82.65	$82.70
7 purchase totals =	$917.47		$1,003.5495	$1,003.56	$1,003.60	$1,003.50