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	$149.29	3.556%	$154.5988	$154.60	$154.60	$154.60
Purchase #2	$187.39	9.617%	$205.4113	$205.41	$205.40	$205.40
Purchase #3	$148.56	7.797%	$160.1432	$160.14	$160.15	$160.10
Purchase #4	$103.53	11.459%	$115.3935	$115.39	$115.40	$115.40
Purchase #5	$227.56	12.284%	$255.5135	$255.51	$255.50	$255.50
Purchase #6	$59.93	8.425%	$64.9791	$64.98	$65.00	$65.00
Purchase #7	$105.94	13.553%	$120.298	$120.30	$120.30	$120.30
7 purchase totals =	$982.20		$1,076.3374	$1,076.33	$1,076.35	$1,076.30